Tunneling variable magnetoresistive memory device and method of operation thereof

Abstract

A magnetoresistive memory device includes a first electrode, a second electrode, and a layer stack between the first electrode and the second electrode. The layer stack can include a ferroelectric material layer and a metamagnetic tunnel junction including a metamagnetic material layer, an insulating barrier layer, and a metallic material layer. Alternatively, the layer stack can include a multiferroic material layer, a metamagnetic material layer, an insulating barrier layer, and a reference magnetization layer.

Description

[0001] Related Applications

[0002] This application claims the benefit of priority to U.S. Non-Provisional Patent Application No. 16 / 853,407, filed April 20, 2020, and U.S. Non-Provisional Patent Application No. 16 / 853,440, filed April 20, 2020, the entire contents of which are hereby incorporated by reference herein for all purposes. TECHNICAL FIELD

[0003] The present disclosure relates generally to the field of magnetoresistive memory devices, and in particular to a tunneling variable magnetoresistive memory device employing electric field induced switching and methods of operation thereof. BACKGROUND

[0004] Magnetoresistive memory devices can store information employing a difference in resistance in a first configuration in which a magnetization direction of a free magnetic layer is parallel to a magnetization of a reference magnetic layer and a second configuration in which the magnetization direction of the free magnetic layer is anti-parallel to the magnetization of the reference magnetic layer. Programming of magnetoresistive memory devices, such as STT-MRAM, typically involves using an external power source to flip the magnetization direction of the free layer using a tunneling current through a magnetic tunnel junction. However, the switching power required to generate the tunneling current is higher than desired. SUMMARY

[0005] According to one aspect of the present disclosure, a magnetoresistive memory device includes a first electrode, a second electrode, and a layer stack located between the first electrode and the second electrode, the layer stack including a ferroelectric material layer and a variable magnetic tunnel junction. The variable magnetic tunnel junction includes a variable magnetic material layer, a metallic material layer, and an insulating barrier layer located between the metallic material layer and the variable magnetic material layer.

[0006] According to another aspect of the present disclosure, a magnetoresistive memory device includes a first electrode, a second electrode, and a layer stack located between the first electrode and the second electrode, the layer stack including a multiferroic material layer and a variable magnetic tunnel junction. The variable magnetic tunnel junction includes a variable magnetic material layer, a reference magnetic layer, and an insulating barrier layer located between the reference magnetic layer and the variable magnetic material layer.

[0007] According to another aspect of the present disclosure, a method of operating any of the magnetoresistive memory devices of the present disclosure is provided, the method including applying a first polarity programming voltage to the first electrode relative to the second electrode in a first programming step to switch a state of the variable magnetic material layer from a non-magnetic state to a magnetic state, and applying a second polarity programming voltage to the first electrode relative to the second electrode in a second programming step to switch the state of the variable magnetic material layer from the magnetic state to the non-magnetic state, the second polarity programming voltage having an opposite polarity to the first polarity programming voltage. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 This is a schematic diagram of a random access memory device including magnetoresistive memory cells of the present disclosure in an array configuration.

[0009] Figure 2 A first exemplary tunneling variable magnetoresistive (TMMR) memory cell according to a first embodiment of the present disclosure is schematically shown.

[0010] Figure 3A A first configuration of a second exemplary tunneling variable magnetoresistive (TMMR) memory cell according to a second embodiment of the present disclosure is schematically shown.

[0011] Figure 3B A second configuration of a second exemplary tunneling variable magnetoresistive (TMMR) memory cell according to a second embodiment of the present disclosure is schematically shown. Detailed Implementation

[0012] As discussed above, embodiments of this disclosure relate to tunneling variable magnetoresistive memory devices employing electric field induction switching and methods of operation thereof, the various aspects of which are described below.

[0013] The accompanying drawings are not to scale. Where a single instance of an element is shown, multiple instances of the element may be repeated unless explicitly described or otherwise clearly indicated that no repetition of an element exists. Numbers such as “first,” “second,” and “third” are used only to identify similar elements and may be used differently throughout the specification and claims of this disclosure. The term “at least one” element refers to all possibilities, including the possibility of a single element and the possibility of multiple elements.

[0014] The same reference numerals denote the same or similar elements. Unless otherwise stated, elements with the same reference numerals are assumed to have the same composition and the same function. Unless otherwise specified, “contact” between elements means direct contact between elements that provide a shared edge or surface. If two or more elements are not in direct contact with each other or with each other, the two elements are “separated” from each other or “separated” from each other. As used herein, a first element positioned “on” a second element may be positioned on the outer side of the surface of the second element or on the inner side of the second element. As used herein, if there is physical contact between the surfaces of the first element and the second element, the first element is positioned “directly” on the second element. As used herein, if there is a conductive path made of at least one conductive material between the first element and the second element, the first element is “electrically connected” to the second element. As used herein, a “prototype” structure or a “process” structure refers to a transient structure in which the shape or composition of at least one of its components is subsequently modified.

[0015] As used herein, a “layer” refers to a portion of material comprising a region having thickness. A layer may extend over the entirety of a lower or upper overlay structure, or may have a range smaller than that of the lower or upper overlay structure. Additionally, a layer may be a region of a uniform or non-uniform continuous structure having a thickness less than that of the first continuous structure. For example, a layer may be positioned between the top and bottom surfaces of the first continuous structure or between any pair of horizontal planes at the top and bottom surfaces of the first continuous structure. A layer may extend horizontally, vertically, and / or along a tapered surface. A substrate may be a layer, and may include one or more layers, or may have one or more layers on, above, and / or below it.

[0016] refer to Figure 1 A schematic diagram of a magnetoresistive random access memory (MRAM) device 500 including a plurality of magnetoresistive memory cells 180 of embodiments of the present disclosure is shown. In one embodiment, the magnetoresistive random access memory device 500 may contain a two-dimensional array or a three-dimensional array of the magnetoresistive memory cells 180 of embodiments of the present disclosure. As used herein, "random access memory device" means a memory device containing memory cells that allow random access, i.e., access to any selected memory cell upon a command to read the contents of a selected memory cell.

[0017] The magnetoresistive random access memory (MRAM) device 500 may include a memory array region 550 containing an array of corresponding magnetoresistive memory cells 180 located at the intersection of corresponding word lines 30 and bit lines 90. The MRAM device 500 may also include a combination of a row decoder 560 connected to the word line 30, programming and sensing circuitry 570 (which may include programming transistors, sense amplifiers, and other bit line control circuitry) connected to the bit line 90, a column decoder 580 connected to the bit line 90 via the programming and sensing circuitry 570, and a data buffer 590 connected to the programming and sensing circuitry 570. Multiple instances of the magnetoresistive memory cells 180 are provided to form an array configuration of the MRAM device 500. Thus, each magnetoresistive memory cell 180 may be a two-terminal device including a corresponding first electrode and a corresponding second electrode. It should be noted that the location and interconnection of components are schematic, and components may be arranged in different configurations. Furthermore, the magnetoresistive memory cells 180 may be manufactured as discrete devices, i.e., single isolated devices.

[0018] refer to Figure 2 This illustration shows a first exemplary magnetoresistive memory device according to a first embodiment of the present disclosure. The first exemplary magnetoresistive memory cell 180 is a tunneling variable magnetoresistive (TMMR) memory cell. The first exemplary magnetoresistive memory device includes the magnetoresistive memory cell 180, which can function as... Figure 1The illustrated TMMR magnetoresistive random access memory (TMMR MRAM) device 500 has a unit memory cell. In this case, multiple magnetoresistive memory cells 180 can be formed in an array configuration, which can be a two-dimensional array configuration or a three-dimensional array configuration. Alternatively, Figure 2 The magnetoresistive memory cell 180 shown can be configured as a discrete memory device connected to corresponding programming and sensing circuits. In other words, each magnetoresistive memory cell 180 can be connected to a corresponding programming and sensing circuit.

[0019] Each magnetoresistive memory cell 180 may include a first electrode 170, a second electrode 270, and a layer stack (280, 240) located between the first electrode 170 and the second electrode 270. The layer stack (280, 240) includes a ferroelectric material layer 280 with non-zero ferroelectric polarization (i.e., polarization) and includes a variable magnetic tunnel junction 240. The variable magnetic tunnel junction 240 is in Figure 2 The diagram shows the ferroelectric material layer 280 located on top of it (i.e., between the ferroelectric material layer 280 and the second electrode 270). However, in an alternative embodiment, the variable magnetic tunnel junction 240 may be located below the ferroelectric material layer 280 (i.e., between the ferroelectric material layer 280 and the first electrode 170). The variable magnetic tunnel junction 240 may contact the surface of the ferroelectric material layer 280.

[0020] In one embodiment, each first electrode 170 may be located on a corresponding word line in word line 30, and each second electrode 270 may be located on a corresponding bit line in bit line 90. Alternatively, each first electrode 170 may be located on a corresponding bit line in bit line 90, and each second electrode 270 may be located on a corresponding word line in word line 30. Alternatively, each electrode (170, 270) may be part of a corresponding word line 30 or bit line 90, rather than a separate layer contacting the corresponding word line or bit line. Word lines 30 may be formed as a one-dimensional array of first metal lines located at a first metal interconnect level and extending laterally along a first horizontal direction, and bit lines 90 may be formed as a one-dimensional array of second metal lines located at a second metal interconnect level and extending laterally along a second horizontal direction, the second horizontal direction being not parallel to (e.g., perpendicular to) the first horizontal direction. In one embodiment, each of the word line 30 and the bit line 90 may include a metal nitride pad, which may include an optional conductive metal nitride material (such as TiN, TaN, or WN) and a metal filler material (such as Cu, W, Co, Ru, Mo, Al, etc.).

[0021] The first electrode 170 may comprise and / or be substantially composed of a conductive metal nitride material or a non-magnetic metallic material comprising at least one transition metal. The at least one transition metal of the non-magnetic metallic material may be selected from Cu, Cr, Ti, Ta, W, Mo, Al, Au, and / or Ru. In this case, the sidewalls of the first electrode 170 may or may not vertically coincide with the sidewalls of the variable magnetic tunnel junction 240. In one embodiment, the thickness of the first electrode 170 may be in the range of 1 nm to 20 nm, such as from 2 nm to 10 nm, although smaller and larger thicknesses are also possible.

[0022] Each layer stack (280, 240) can be formed, for example, by depositing a set of continuous material layers and patterning the set of continuous material layers by a combination of photolithographic patterning and anisotropic etching processes or by a focused ion beam etching process. Each layer stack (280, 240) may optionally include a set of sidewalls that are vertically overlapping each other. As used herein, if one of the two surfaces overlies or lies beneath the other of the two surfaces, and if there is a vertical plane containing the two surfaces, then the two surfaces are "vertically overlapping". Word lines 30, a two-dimensional array of magnetoresistive memory cells 180, and bit lines 90 can be embedded within an interconnect-level dielectric material layer 20 formed above a substrate 10, which may be a semiconductor substrate such as a silicon substrate or an insulating substrate such as a sapphire substrate.

[0023] The ferroelectric material layer 280 may include and / or consist substantially of at least one ferroelectric dielectric material, such as hafnium oxide (e.g., hafnium oxide containing at least one dopant selected from Al, Zr, and Si and having a ferroelectric non-centrosymmetric orthorhombic crystal system), zirconium oxide, hafnium oxide-zirconium oxide, bismuth ferrite, barium titanate (e.g., BaTiO3; BT), and calcareous borate (e.g., Ca2B6O3). 11 5H2O), bismuth titanate (such as Bi4Ti3O) 12 ), barium europium titanate, ferroelectric polymers, germanium telluride, anhydrous potassium magnesium vanadium (such as M2M′2(SO4)3, where M is a monovalent metal and M' is a divalent metal), lead scandium tantalate (such as Pb(Sc) x Ta 1-x Lead titanate (such as PbTiO3; PT), lead zirconate titanate (such as Pb(Zr,Ti)O3; PZT), lithium niobate (such as LiNbO3; LN), lanthanum oxide (LaAlO3), polyvinylidene fluoride (CH2CF2)n, potassium niobate (such as KNbO3), potassium sodium tartrate (such as KNaC4H4O64H2O), potassium oxytitanium phosphate (such as KO5PTi), sodium bismuth titanate (such as Na 0.5 Bi 0.5 TiO3 or Bi 0.5 Na 0.5TiO3), lithium tantalate (LiTaO3(LT)), lead lanthanum titanate (such as (Pb,La)TiO3(PLT)), lead lanthanum zirconate titanate (such as ((Pb,La)(Zr,Ti)O3(PLZT)), ammonium dihydrogen phosphate (such as NH4H2PO4(ADP)) or potassium dihydrogen phosphate (such as KH2PO4(KDP)).

[0024] The variable magnetic tunnel junction 240 may include being positioned in contact with the ferroelectric material layer 280 (e.g., in...). Figure 2 A variable magnetic material layer 236 (located on top of the layer) is included. As used herein, "variable magnetic material" refers to a material having both a non-magnetic state and a magnetic state. As used herein, "variable magnetic tunnel junction" refers to a tunnel junction including a variable magnetic material layer (i.e., a layer substantially composed of variable magnetic material). The magnetic state of the variable magnetic material can be a ferromagnetic state, a ferrimagnetic state, or an antiferromagnetic state with non-zero net magnetization. The non-magnetic state can be a paramagnetic state or an antimagnetic state. In one embodiment, the variable magnetic material layer 236 may include and / or be substantially composed of a material selected from the group consisting of Co, FeRh alloys, EuSe alloys, CrO2, and / or lanthanum strontium manganese oxide ("LSM", e.g., La). 1-x Sr x MnO3).

[0025] The insulating barrier layer 134 includes an insulating tunneling barrier material for forming a variable magnetic tunnel junction. The insulating barrier layer 134 may include, for example, magnesium oxide, aluminum oxide, strontium titanate, or combinations thereof. The thickness of the insulating barrier layer 134 may be thin enough to allow tunneling current to flow through it, such as a thickness in the range of 0.5 nm to 2 nm, such as from 0.7 nm to 1.2 nm, although smaller and larger thicknesses may also be used.

[0026] The metal material layer 232 may comprise any metallic material that does not affect the transition between magnetic and nonmagnetic states within the variability magnetic material layer 236. In one embodiment, the metal material layer 232 comprises a non-ferromagnetic metallic material, i.e., a metallic material that does not have a ferromagnetic state. In another embodiment, the metal material layer 232 comprises a non-magnetic metallic material, i.e., a metallic material that does not have a ferromagnetic, subferromagnetic, or antiferromagnetic state. For example, the metal material layer 232 may comprise Cu, Cr, Ti, Ta, Au, and / or Ru. The thickness of the metal material layer 232 may range from 1 nm to 10 nm, such as from 2 nm to 5 nm, although smaller and larger thicknesses are also possible.

[0027] In one embodiment, the second electrode 270 may include a nonmagnetic capping layer located on the metallic material layer 232. For example, if the metallic material layer 232 includes Cr, the capping layer may include and / or may consist substantially of Ru and / or Ta. Alternatively, the second electrode 270 may include at least one nonmagnetic transition metal selected from Cu, Cr, Ti, Ta, W, Mo, Al, Au, and / or Ru.

[0028] The sidewall of the second electrode 270 may or may not be vertically aligned with the sidewall of the variable magnetic tunnel junction 240. The thickness of the second electrode 270 may be in the range of 1 nm to 20 nm, such as from 2 nm to 10 nm, although smaller and larger thicknesses are also possible.

[0029] In an alternative embodiment, the first electrode 170 may include a portion of a word line 30 that overlaps with a region of the variable magnetic tunnel junction 240 and is in direct contact with the surface of the ferroelectric material layer 280. Additionally or alternatively, the second electrode 270 may include a portion of a bit line 90 that overlaps with a region of the variable magnetic tunnel junction 240 and is in direct contact with the surface of the metallic material layer 232.

[0030] The magnetoresistive memory device 180 of the first embodiment includes a first electrode 170, a second electrode 270, and a layer stack (240, 280) located between the first electrode and the second electrode. The layer stack includes a ferroelectric material layer 280 and a variable magnetic tunnel junction 240. The variable magnetic tunnel junction 240 includes a variable magnetic material layer 236, a metal material layer 232, and an insulating barrier layer 134 located between the metal material layer and the variable magnetic material layer.

[0031] According to the embodiments of this disclosure, the variable magnetic material layer 136 can directly contact the ferroelectric material layer 280 and the insulating barrier layer 134.

[0032] According to embodiments of this disclosure, the variable magnetic tunnel junction 240 has different tunneling magnetoresistances between a first state in which the variable magnetic material layer 236 is in a non-magnetic state and a second state in which the variable magnetic material layer 236 is in a magnetic state. The different tunneling magnetoresistances between the first and second states can be caused by the contraction of tunneling current due to the available electron surface states at the interface between the variable magnetic material layer 236 and the insulating barrier layer 134. In one embodiment, the variable magnetic material of the variable magnetic material layer 236 may have a variable surface density of states at the interface interacting with the insulating barrier layer 134, which changes between the non-magnetic state and the magnetic state of the variable magnetic material. In one embodiment, the variable magnetic tunnel junction 240 has a variable tunneling resistance that increases as the variable surface density of the states of the variable magnetic material of the variable magnetic material layer 236 at the interface interacting with the insulating barrier layer 134 decreases.

[0033] In one embodiment, the magnetic states of the variable magnetic material layer 236 include a ferromagnetic state, a hypoferromagnetic state, or an antiferromagnetic state, and the non-magnetic states of the variable magnetic material layer 236 include a paramagnetic state or an antimagnetic state. In one embodiment, the variable magnetic material layer 236 has a first surface density in the magnetic state and a second surface density in the non-magnetic state. The ratio of the first surface density to the second surface density can be at a level detectable by a sensing circuit connected to the magnetoresistive memory cell 180. For example, the ratio of the first surface density to the second surface density can be in the range of 0.1 to 0.95, such as from 0.2 to 0.75, or in the range of 1.05 to 10, such as from 1.33 to 5. The ratio of the first surface density to the second surface density depends on the nature of the change in surface electronic states at the interface between the variable magnetic material layer 236 and the insulating barrier layer 134.

[0034] In one embodiment, the ferroelectric material layer 280 includes two bistable polarization directions for non-zero polarization. Alignment of the non-zero polarization along one of the two bistable polarization directions induces a magnetic state in the variable magnetic material layer 236, and alignment of the non-zero polarization along the other of the two bistable polarization directions induces a non-magnetic state in the variable magnetic material layer 236. In one embodiment, the two bistable polarization directions of the non-zero polarization of the ferroelectric material layer 280 may be opposite directions, i.e., antiparallel to each other. In one embodiment, the two bistable polarization directions may form a non-zero angle with respect to the interface between the ferroelectric material layer 280 and the variable magnetic material layer 236. In one embodiment, the two bistable polarization directions may form an angle ranging from 30 degrees to 90 degrees with respect to the interface between the ferroelectric material layer 280 and the variable magnetic material layer 236, such as from 60 degrees to 90 degrees.

[0035] In one embodiment, the first exemplary magnetoresistive memory device may include a programming circuit system comprising a line decoder 560 and programming and sensing circuitry 570. The programming circuit system is configured to apply a first programming voltage pulse of a first polarity between a first electrode 170 and a second electrode 270 to program a variable magnetic material layer 236 into a magnetic state, and to apply a second programming pulse of a second polarity opposite to the first polarity between the first and second electrodes 170 to program the variable magnetic material layer 236 into a non-magnetic state. Specifically, the programming voltage pulse may change the polarization direction of a ferroelectric material layer 280. The polarization direction of the ferroelectric material layer 280 then causes the variable magnetic material layer 236 to change between a magnetic state and a non-magnetic state, or vice versa. In one embodiment, the first polarity may provide a more positive voltage to the first electrode 170 relative to the second electrode 270, and the second polarity may provide a more negative voltage to the first electrode 170 relative to the second electrode 270. In another embodiment, the first polarity may provide a more negative voltage to the first electrode 170 relative to the second electrode 270, and the second polarity may provide a more positive voltage to the first electrode 170 relative to the second electrode 270.

[0036] Therefore, the applied voltage can be used to change the state of the variable magnetic material layer 236 without generating a tunneling current through the junction 240. This reduces the amount of power required to change the resistivity of the memory cell 180. The correspondence between the specific polarization direction of the ferroelectric material layer 280 and the magnetic or non-magnetic state of the variable magnetic material layer 236 depends on the specific materials of layers 280 and 236.

[0037] In an exemplary example, the ferroelectric material layer 280 comprises HfO2 or BaTiO3 and has a thickness ranging from 1 nm to 5 nm; the variable magnetic material layer 236 comprises a cobalt layer or FeRh layer having a thickness ranging from 1 nm to 3 nm; the insulating barrier layer 134 comprises a magnesium oxide layer having a thickness ranging from 1 nm to 3 nm; and the metallic material layer 232 comprises a TiN layer or tungsten layer having a thickness ranging from 2 nm to 5 nm. In this case, the first programming pulse may have a value ranging from 0.5 V to 3.0 V, and the second programming pulse may have a value ranging from -0.5 V to -3.0 V. The duration of each programming pulse in the first and second programming pulses may be in the range of 0.1 ns to 100 ns, such as from 1 ns to 10 ns, but smaller and larger pulse durations may also be used. The programming and sensing circuit 570 may be configured to apply a sensing pulse having a value ranging from 0.1 V to 0.5 V.

[0038] In one embodiment, a magnetoresistive random access memory (MRAM) is provided, comprising: a two-dimensional array of instances of a first exemplary magnetoresistive memory cell 180; word lines 30 electrically connected to a corresponding subset of first electrodes 170 of the two-dimensional array; bit lines 90 electrically connected to a corresponding subset of second electrodes 270 of the two-dimensional array; a row decoder 560; and programming and sensing circuitry 570 connected to the word lines 30 and the bit lines 90 and configured to program one or more magnetoresistive memory cells in the first exemplary magnetoresistive memory cell 180.

[0039] In one implementation scheme Figure 2 The first exemplary magnetoresistive memory device can be programmed to switch the state of the variable magnetic material layer 236 from a non-magnetic state to a magnetic state by applying a first polarity programming voltage relative to the second electrode 270 to the first electrode 170 in a first programming step, and / or to switch the state of the variable magnetic material layer 236 from a magnetic state to a non-magnetic state by applying a second polarity programming voltage having the opposite polarity to the first polarity programming voltage relative to the second electrode 270 to the first electrode 170 in a second programming step.

[0040] In one embodiment, a first polarity programming voltage changes the polarization direction of the ferroelectric material layer from a first direction to a second direction, causing the variable magnetic material layer state to change from a non-magnetic state to a magnetic state. A second polarity programming voltage changes the polarization direction of the ferroelectric material layer from the second direction to the first direction, causing the variable magnetic material layer state to change from a magnetic state to a non-magnetic state. In one embodiment, the state of the variable magnetic material layer 236 can be sensed by measuring the tunneling magnetoresistance of the variable magnetic tunnel junction 240. The tunneling magnetoresistance can vary from 40% to 150% between the two states of the variable magnetic material layer 236.

[0041] refer to Figure 3A and Figure 3B The second exemplary tunneling variable magnetoresistive (TMMR) memory cell 180 according to a second embodiment of the present disclosure is shown. Figure 3A A first configuration of the second exemplary structure is shown, and Figure 3B A second configuration of the second exemplary structure is shown, both configurations including a multiferroic material layer 380 replacing the ferroelectric material layer 280. The second exemplary magnetoresistive memory device may include magnetoresistive memory cells 180 that can serve as unit memory cells of a magnetoresistive random access memory device 500. In this case, a plurality of magnetoresistive memory cells 180 may be formed in an array configuration, which may be a two-dimensional array configuration or a three-dimensional array configuration. Alternatively, Figure 3A and Figure 3BThe magnetoresistive memory cell 180 shown can be configured as a discrete memory device connected to corresponding programming and sensing circuits. In other words, each magnetoresistive memory cell 180 can be connected to a corresponding programming and sensing circuit.

[0042] Each magnetoresistive memory cell 180 includes a first electrode 170, a second electrode 270, and a layer stack (380, 340) located between the first electrode 170 and the second electrode 270. The first electrode and the second electrode (170, 270), as well as the word line and bit line (30, 90), may be the same as in the first embodiment and will be described in more detail below.

[0043] The stacked layers (380, 340) include a multiferroic material layer 380 and a variable magnetic tunnel junction 340. As used herein, a "multiferroic" material means a material exhibiting at least two of ferromagnetic ordering (such as ferromagnetism, antiferromagnetism, or ferrimagnetism), ferroelectricity, and ferroelasticity. As used herein, "magnetoelectric multiferroic" means a material exhibiting both ferromagnetic ordering and ferroelectricity. In a magnetoelectric multiferroic material, a change in total magnetization is coupled with a change in total polarization, and thus a magnetic transition can be coupled to a change in polarization and vice versa.

[0044] Variable magnetic tunnel junction 340 Figure 3A and Figure 3B The diagram shows the multiferroic material layer 380 located on top of it (i.e., between the multiferroic material layer 380 and the second electrode 270). However, in an alternative embodiment, the variable magnetic tunnel junction 340 may be located below the multiferroic material layer 380 (i.e., between the multiferroic material layer 380 and the first electrode 170). The variable magnetic tunnel junction 340 may contact the surface of the multiferroic material layer 380.

[0045] The variable magnetic tunnel junction 340 includes a variable magnetic material layer 236 positioned in contact with a multiferroic material layer 380 and comprising a material having a non-magnetic state and a magnetic state, an insulating barrier layer 134 located on the variable magnetic material layer 236, and a reference magnetization layer 132 located on the insulating barrier layer 134 and having a fixed magnetization direction. The variable magnetic tunnel junction 340 can contact the surface of the multiferroic material layer 380.

[0046] In one embodiment, the multiferroic material layer 380 may include and / or may consist substantially of a magnetoelectric multiferroic material exhibiting ferromagnetic type order and ferroelectricity. Therefore, the multiferroic material layer 380 has non-zero polarization. In a magnetoelectric multiferroic material, changes in total magnetization are coupled with changes in total polarization, and thus magnetic transitions can be coupled to changes in polarization and vice versa.

[0047] In one embodiment, the multiferroic material layer 380 comprises and / or is substantially composed of a multiferroic material, wherein the relative orientation between the non-zero polarization and the net magnetization of the multiferroic material layer 380 remains unchanged when the direction of the non-zero polarization of the multiferroic material layer 380 is reversed. In one embodiment, the magnetization of the multiferroic material layer 380 has a bistable configuration, wherein a first magnetization direction and a second magnetization direction are stable directions for magnetizing the multiferroic material layer, and the second magnetization direction is antiparallel to the first magnetization direction.

[0048] In an exemplary example, the relative orientation between the non-zero polarization of the BiFeO3 multiferroic material and the net magnetization of BiFeO3 remains unchanged when the direction of the non-zero polarization of BiFeO3 is reversed. In one embodiment, the multiferroic material layer 380 may include a material selected from the following: BiFeO3, h-YMnO3, BaNiF4, PbVO3, BiMnO3, LuFe2O4, HoMn2O5, h-HoMnO3, h-ScMnO3, h-ErMnO3, h-TmMnO3, h-YbMnO3, h-LuMnO3, K2SeO4, Cs2CdI4, TbMnO3, Ni3V2O8, MnWO4, CuO, ZnCr2Se4, LiCu2O2, and Ni3B7O. 13 I. The thickness of the multiferroic material layer 380 can range from 1 nm to 10 nm, such as from 2 nm to 5 nm, although smaller and larger thicknesses are also possible.

[0049] The variable magnetic tunnel junction 340 may include a variable magnetic material layer 236 positioned in contact with the multiferroic material layer 380 (e.g., located on the variable magnetic material layer). In one embodiment, the magnetic state of the variable magnetic material of the variable magnetic tunnel junction 340 may be a ferromagnetic state with a non-zero net magnetization. The nonmagnetic state may be a paramagnetic state or an antimagnetic state. In one embodiment, the variable magnetic material layer 236 may include and / or consist substantially of a material selected from the group consisting of Co, FeRh alloys, EuSe alloys, CrO2, and / or LSM.

[0050] The insulating barrier layer 134 includes an insulating barrier material for forming a variable magnetic tunnel junction. The insulating barrier layer 134 may include, for example, magnesium oxide, aluminum oxide, strontium titanate, or combinations thereof. The thickness of the insulating barrier layer 134 may range from 0.5 nm to 2.0 nm, such as from 0.7 nm to 1.2 nm, although smaller and larger thicknesses are also possible.

[0051] The reference magnetization layer 132 may comprise a ferromagnetic material with perpendicular magnetic anisotropy. The reference magnetization layer 132 comprises a material that can provide high perpendicular magnetic anisotropy. Therefore, the magnetization direction of the reference magnetization layer 132 is vertical, i.e., perpendicular to the interface between contact layers within the variable magnetic tunnel junction 340. The ferromagnetic material of the reference magnetization layer 132 does not need to generate any spin polarization current.

[0052] In one embodiment, the reference magnetization layer 132 comprises a material selected from the following: FePt alloys, FePd alloys, CoPt alloys, Pt / Co multilayer stacks, Co / Ag multilayer stacks, Co / Cu multilayer stacks, Co / Ni multilayer stacks, (Pt / Co / Pt) / Pd multilayer stacks, (Pt / Co / Pt) / Ag multilayer stacks, (Pt / Co / Pt) / Cu multilayer stacks, (Pt / Co / Pt) / Ni multilayer stacks, and Co / (Pt / Pd) multilayer stacks. In an exemplary example, the reference magnetization layer 132 may comprise an L10 alloy of FePt, FePd, or CoPt disclosed in the *Journal of Applied Physics*, 111, 07A708 (2012). The FePt alloy, FePd alloy, and CoPt alloy may each have a 6.6 × 10⁻⁶ Ω·cm² content. 7 erg / cm 3 1.8×10 7 erg / cm 3 and 4.9×10 7 erg / cm 3 The magnetic anisotropy constant. In another exemplary example, the reference magnetization layer 132 may comprise a Pt / Co multilayer, Co / Ag multilayer, Co / Cu multilayer, or Co / Ni multilayer disclosed in IEEE Transactions on Magnitics, 31, 3337, (1995), or may comprise a (Pt / Co / Pt) / Pd multilayer, (Pt / Co / Pt) / Ag multilayer, (Pt / Co / Pt) / Cu multilayer, or (Pt / Co / Pt) / Ni multilayer. In yet another exemplary example, the reference magnetization layer 132 may comprise a Co / (Pt / Pd) multilayer or a Co / (Pd / Pt) multilayer disclosed in the Journal of Applied Physics, 77, 3995 (1995). Alternatively, the reference magnetization layer 132 may comprise an Fe layer, a Co layer, a Ni layer, a CoFeB layer, a CoFe layer, a Co / Ni multilayer structure, or a Co / Pt multilayer structure. The reference magnetization layer 132 may have a thickness of 2 nm to 10 nm, such as 3 nm to 6 nm.

[0053] In a first configuration of the second exemplary structure, a synthetic antiferromagnetic (SAF) structure 320 may be provided. In this case, the SAF structure 320 includes a layer stack that includes a reference magnetization layer 132, an antiferromagnetic coupling layer 114, and a fixed magnetization layer 112 from one side to the other.

[0054] The reference magnetization layer 132 may comprise any soft ferromagnetic material, such as CoFe or CoFeB. The antiferromagnetic coupling layer 114 may comprise an antiferromagnetic coupling material, such as a multilayer stack of ruthenium, iridium, iridium-manganese alloy, or cobalt and platinum layers, and may have a thickness ranging from 0.5 nm to 2 nm. The thickness of the antiferromagnetic coupling layer 114 may be optimized to maximize the antiferromagnetic coupling between the reference magnetization layer 132 and the fixed magnetization layer 112.

[0055] The fixed magnetization layer 112 is spaced apart from the reference magnetization layer 132 and may include any material that can be used for the reference magnetization layer 132. The thickness of the fixed magnetization layer 112 may be in the range of 2 nm to 10 nm, such as 3 nm to 6 nm. The antiferromagnetic coupling layer 114 antiferromagnetically couples the fixed magnetization of the reference magnetization layer 132 to the magnetization of the fixed magnetization layer 112. Therefore, the fixed magnetization of the reference magnetization layer 132 is antiparallel to the magnetization of the fixed magnetization layer 112.

[0056] exist Figure 3B In the second configuration of the second exemplary structure shown, any hard magnetic material that can provide high perpendicular magnetic anisotropy can be used for the reference magnetization layer 132. In this embodiment, the SAF structure 320 is omitted.

[0057] In one embodiment, the second electrode 270 may include a capping layer located on the metallic material layer 232. In this case, the second electrode 270 may include and / or may be substantially composed of Ru and / or Ta. Alternatively, the second electrode 270 may include at least one nonmagnetic transition metal selected from the following: Cu, Cr, Ti, Ta, W, Mo, Al, Au and / or Ru.

[0058] exist Figure 3A In the first configuration shown, the second electrode 270 can contact the fixed magnetization layer 112 of the SAF structure 320. Figure 3B In the second configuration shown, the second electrode 270 can contact the reference magnetization layer 132.

[0059] In an alternative embodiment, the first electrode 170 may include a portion of a word line 30 that overlaps with a region of the variable magnetic tunnel junction 340 and directly contacts the surface of the multiferroic material layer 380. Additionally or alternatively, the second electrode 270 may include a portion of a bit line 90 that overlaps with a region of the variable magnetic tunnel junction 340 and directly contacts the surface of the metallic material layer 232.

[0060] According to embodiments of this disclosure, the multiferroic material layer 380 has a non-zero polarization coupled to the magnetization of the multiferroic material layer 380. A programming voltage pulse applied between the first electrode and the second electrode (170, 270) alters the polarization direction of the multiferroic material layer 380, causing a corresponding change in the magnetization direction of the multiferroic material layer 380. In one embodiment, the multiferroic material layer 380 is magnetically coupled to a variable magnetic material layer 236, and the change in the magnetization direction in the multiferroic material layer 380 induces a transition between a magnetic state and a non-magnetic state in the variable magnetic material layer 236. Therefore, the resistivity state of the variable magnetic tunnel junction 340 can be changed solely by the applied programming voltage pulse without generating a tunneling current through the junction 340.

[0061] In summary, the ferroelectric properties of multiferroic materials induce ferromagnetism in variadic materials. Furthermore, the magnetic properties of multiferroic materials will align the ferromagnetic spins of the magnetic states in variadic materials in one of two directions. Therefore, the magnetization direction of the multiferroic material layer 380 is coupled to the direction of its non-zero polarization. A change in the direction of the non-zero polarization of the multiferroic material layer 380 induces a change in the magnetization direction within the multiferroic material layer 380. The direction of the non-zero polarization of the multiferroic material layer 380 can be changed by applying an external voltage between the first electrode 170 and the second electrode 270, which generates an electric field either upward or downward along the vertical direction, depending on the polarity of the external voltage. When a sufficient voltage is applied in either direction, the vertical component of the non-zero polarization of the multiferroic material layer 380 is aligned with the vertical direction of the electric field within the multiferroic material layer 380. One of the first and second magnetization directions of the multiferroic material layer 380 induces a magnetic state within the variable magnetic material layer 236, and the other magnetization direction induces a nonmagnetic state within the variable magnetic material layer 236. In one embodiment, the magnetic state includes a ferromagnetic state having a magnetization direction aligned with one of the first or second magnetization directions. The specific direction depends on the materials of layers 380 and 236.

[0062] The magnetoresistive memory device 180 of the second embodiment includes a first electrode 170, a second electrode 270, and a layer stack (340, 380) located between the first electrode and the second electrode. The layer stack includes a multiferroic material layer 380 and a variable magnetic tunnel junction 340. The variable magnetic tunnel junction 340 includes a variable magnetic material layer 236, a reference magnetization layer 132, and an insulating barrier layer 134 located between the reference magnetization layer and the variable magnetic material layer.

[0063] In one embodiment, the variable magnetic material layer 236 physically contacts the multiferroic material layer 280 and the insulating barrier layer 134.

[0064] In one embodiment, the magnetic state of the variable magnetic material layer 236 includes the ferromagnetic state of the variable magnetic material layer 236. In one embodiment, the reference magnetization layer 132 includes a fixed magnetization direction oriented along the vertical component of the magnetization direction antiparallel to the magnetization direction of the ferromagnetic state of the variable magnetic material layer 236.

[0065] Typically, a tunnel junction having two ferromagnetic material layers with antiferromagnetic magnetization alignment provides a higher tunneling resistance than a tunnel junction where one of the two ferromagnetic material layers is replaced by a nonmagnetic metallic material having the same electrical conductivity as the replaced ferromagnetic material layer. The variable magnetic tunnel junction 340 has a first state (a low-resistance state) in which the variable magnetic material layer 236 is in a nonmagnetic state. The variable magnetic tunnel junction 340 has a second state (a high-resistance state) in which the variable magnetic material layer 236 is in a ferromagnetic state having a magnetization direction antiparallel to the magnetization direction of the reference magnetization layer 132.

[0066] The first state provides a first tunneling magnetic reluctance, and the second state provides a second, higher tunneling magnetic reluctance. In other words, the variable magnetic tunnel junction 340 may have a first tunneling magnetic reluctance when the variable magnetic material layer 236 is in a non-magnetic state, and a second, higher tunneling magnetic reluctance when the variable magnetic material layer 236 is in a magnetic state. In one embodiment, the second tunneling magnetic reluctance is at least 105% of the first tunneling magnetic reluctance. For example, the ratio of the second tunneling magnetic reluctance to the first tunneling magnetic reluctance may be in the range of 1.05 to 6, such as from 2 to 6.

[0067] The second exemplary magnetoresistive memory cell 180 is a tunneling variable magnetoresistive (TMMR) memory cell. The magnetic state of the variable magnetic material layer 236 in the second exemplary magnetoresistive memory cell 180 may include a ferromagnetic state, provided that the magnetic state of the variable magnetic material layer 236 provides a tunneling magnetoresistive state different from the non-magnetic state of the variable magnetic material layer 236 in the second exemplary magnetoresistive memory cell 180. Typically, the non-magnetic state of the variable magnetic material layer 236 includes a paramagnetic state or an antimagnetic state.

[0068] In one embodiment, the second exemplary magnetoresistive memory device may include programming circuitry including a line decoder 560 and programming and sensing circuitry 570. The programming circuitry is configured to apply a first programming pulse of a first polarity between a first electrode 170 and a second electrode 270 to program the variable magnetic material layer 236 into a magnetic state, and to apply a second programming pulse of the opposite polarity across the first and second electrodes 170 and 270 to program the variable magnetic material layer 236 into a non-magnetic state. The transition between the magnetic and non-magnetic states of the variable magnetic material layer 236 can be induced by a change in the direction of the non-zero polarization within the multiferroic material layer 380 during the application of the first or second programming pulse.

[0069] In one embodiment, the first polarity may provide a more positive voltage to the first electrode 170 relative to the second electrode 270, and the second polarity may provide a more negative voltage to the first electrode 170 relative to the second electrode 270. In another embodiment, the first polarity may provide a more negative voltage to the first electrode 170 relative to the second electrode 270, and the second polarity may provide a more positive voltage to the first electrode 170 relative to the second electrode 270.

[0070] In an exemplary example, the multiferroic material layer 380 comprises BaTiO3 and has a thickness ranging from 1 nm to 5 nm, the variable magnetic material layer 236 comprises a cobalt layer or FeRh layer having a thickness ranging from 1 nm to 3 nm, the insulating barrier layer 134 comprises a magnesium oxide layer having a thickness ranging from 1 nm to 3 nm, and the reference magnetization layer 132 comprises a CoFe layer or CoFeB layer having a thickness ranging from 1 nm to 2 nm. In this case, the first programming pulse may have a value ranging from 0.5 V to 3 V, and the second programming pulse may have a value ranging from -0.5 V to -3 V. The duration of each programming pulse in the first and second programming pulses may be in the range of 0.1 ns to 100 ns, such as from 1 ns to 10 ns, but smaller and larger pulse durations may also be used. The programming and sensing circuit 570 may be configured to apply a sensing pulse having a value ranging from 0.1 V to 0.5 V.

[0071] In one embodiment, a magnetoresistive random access memory (MRAM) is provided, comprising a two-dimensional array of second exemplary magnetoresistive memory cells 180, word lines 30 electrically connected to a corresponding subset of first electrodes 170 of the two-dimensional array, bit lines 90 electrically connected to a corresponding subset of second electrodes 270 of the two-dimensional array, programming and sensing circuitry 570 connected to the bit lines 90, and a line decoder 560 connected to the word lines 30 and configured to program the corresponding set of exemplary magnetoresistive memory cells 180.

[0072] In the second implementation scheme, Figure 3A and Figure 3B The second exemplary magnetoresistive memory device can be programmed to switch the state of the variable magnetic material layer 236 from a non-magnetic state to a magnetic state by applying a first polarity programming voltage relative to the second electrode 270 to the first electrode 170 in a first programming step, and / or to switch the state of the variable magnetic material layer 236 from a magnetic state to a non-magnetic state by applying a second polarity programming voltage having the opposite polarity to the first electrode 170 relative to the second electrode 270 in a second programming step. In one embodiment, the state of the variable magnetic material layer 236 can be sensed by measuring the tunneling magnetoresistance of the variable magnetic tunnel junction 240.

[0073] Various embodiments of this disclosure provide a magnetoresistive memory device comprising a variable magnetic material layer 236 located at a variable magnetic tunneling junction providing tunneling variable magnetoresistive (TMMR) that changes with the magnetic state of the variable magnetic material layer 236. A potential mechanism for the change in TMMR could be a change in the surface density of the state at the interface between the variable magnetic material layer 236 and the insulating barrier layer 134, occurring concurrently with a magnetic phase transition within the variable magnetic material layer 236, as in the first embodiment. Figure 2 The same applies to the first exemplary TMMR memory device. Alternatively, a potential mechanism for TMMR alteration could be a change in electron tunneling efficiency between a nonmagnetic state of the variable magnetic material layer 236 where electron spin is inactive and a magnetic state where the antiparallel magnetization alignment of the variable magnetic material layer 236 with the reference magnetization layer 132 reduces electron tunneling efficiency, as in the second embodiment. Figure 3A and Figure 3B The same applies to the second exemplary TMMR memory device. In both embodiments, only the applied voltage is used to switch the resistive state of the memory cell without using the tunneling current through the junction (240, 340). Therefore, lower switching energy can be used to deterministically program TMMR MRAM memory cells with relatively high TMR (e.g., 500% to 600%). In contrast, prior art STT MRAM requires higher switching energy and tunneling current for programming, while prior art VCMA MRAM uses the applied voltage to nondeterministically program the memory cell.

[0074] While specific preferred embodiments have been mentioned above, it will be understood that this disclosure is not limited thereto. Those skilled in the art will appreciate that various modifications can be made to the disclosed embodiments, and such modifications are intended to fall within the scope of this disclosure. While embodiments employing specific structures and / or configurations are shown in this disclosure, it should be understood that this disclosure can be practiced with any other functionally equivalent compatible structures and / or configurations, provided that such substitutions are not expressly prohibited or otherwise considered impossible by those skilled in the art. All publications, patent applications, and patents cited herein are incorporated herein by reference in their entirety.

Claims

1. A magnetoresistive memory device, the magnetoresistive memory device comprising: First electrode; Second electrode; and A layer stack, located between the first electrode and the second electrode, the layer stack including a ferroelectric material layer and a variable magnetic tunnel junction, wherein the variable magnetic tunnel junction includes: Variable magnetic material layer; Metallic material layer; An insulating barrier layer, wherein the insulating barrier layer is located between the metallic material layer and the variable magnetic material layer; and At least one feature, said at least one feature includes: (a) First feature, wherein: The ferroelectric material layer includes two bistable polarization directions; Alignment of non-zero polarization along one of the two bistable polarization directions induces a magnetic state in the variable magnetic material layer; and Alignment of the non-zero polarization along the other polarization direction of the two bistable polarization directions induces a nonmagnetic state in the variable magnetic material layer; or (b) a second feature, wherein the metallic material layer comprises a non-magnetic metallic material; or (c) The third feature, wherein the ferroelectric material layer comprises a material selected from the following: hafnium oxide, zirconium oxide, hafnium-zirconium oxide, bismuth ferrite, barium titanate, calcium borate, bismuth titanate, europium barium titanate, ferroelectric polymer, germanium telluride, anhydrous potassium magnesium sulfate, lead scandium tantalate, lead titanate, lead zirconate titanate, lithium niobate, lanthanum aluminate, polyvinylidene fluoride, potassium niobate, potassium sodium tartrate, potassium titanate oxytitanium phosphate, sodium bismuth titanate, lithium tantalate, lead lanthanum titanate, lead lanthanum zirconate titanate, ammonium dihydrogen phosphate, or potassium dihydrogen phosphate; or (d) Fourth feature, wherein the variable magnetic material layer comprises a material selected from the following: Co, FeRh alloy, EuSe alloy, CrO2, or LaSrMnO3; or (e) Fifth feature, wherein the insulating barrier layer comprises a material selected from the group consisting of magnesium oxide, aluminum oxide, strontium titanate, or combinations thereof; or (f) The sixth feature includes a programming circuit, which is configured to: A first programming pulse of first polarity is applied between the first electrode and the second electrode to program the variable magnetic material layer into a magnetic state; and A second programming pulse with a second polarity opposite to the first polarity is applied between the first electrode and the second electrode to program the variable magnetic material layer into a non-magnetic state.

2. The magnetoresistive memory device according to claim 1, wherein the variable magnetic material layer contacts the ferroelectric material layer and the insulating barrier layer.

3. The magnetoresistive memory device according to claim 2, wherein the variable magnetic tunnel junction has different tunneling magnetoresistance between a first state in which the variable magnetic material layer is in a non-magnetic state and a second state in which the variable magnetic material layer is in a magnetic state.

4. The magnetoresistive memory device of claim 3, wherein the variable magnetic material has a variable surface density of state at the interface interacting with the insulating barrier layer, the variable surface density of state changing between the nonmagnetic state of the variable magnetic material and the magnetic state of the variable magnetic material.

5. The magnetoresistive memory device according to claim 4, wherein: The magnetic state of the variable magnetic material layer includes a ferromagnetic state, a subferromagnetic state, or an antiferromagnetic state; and The nonmagnetic state of the variable magnetic material layer includes a paramagnetic state or an antimagnetic state.

6. The magnetoresistive memory device of claim 4, wherein the variable magnetic tunnel junction has a variable tunneling resistance that increases as the variable surface density of the variable magnetic material at the interface interacting with the insulating barrier layer decreases.

7. The magnetoresistive memory device according to claim 4, wherein: The variable magnetic material layer has a first surface density in the magnetic state; and The variable magnetic material layer has a second surface density in the non-magnetic state, which is different from the first surface density in the non-magnetic state.

8. The magnetoresistive memory device of claim 1, wherein the at least one feature includes the first feature.

9. The magnetoresistive memory device of claim 8, wherein the two bistable polarization directions form a non-zero angle with respect to the interface between the ferroelectric material layer and the variable magnetic material layer.

10. The magnetoresistive memory device of claim 1, wherein the at least one feature includes the second feature.

11. The magnetoresistive memory device of claim 1, wherein the metallic material comprises Cu, Cr, Ti, Ta, Au, or Ru.

12. The magnetoresistive memory device of claim 11, wherein the second electrode comprises a Ru or Ta capping layer located on the metal material layer.

13. The magnetoresistive memory device of claim 1, wherein the at least one feature includes the third feature.

14. The magnetoresistive memory device of claim 1, wherein the at least one feature includes the fourth feature.

15. The magnetoresistive memory device of claim 1, wherein the at least one feature includes the fifth feature.

16. The magnetoresistive memory device of claim 1, wherein the at least one feature includes the sixth feature.

17. A magnetoresistive random access memory device, wherein the magnetoresistive random access memory device include: A two-dimensional array of an example of a magnetoresistive memory device according to claim 1; Word lines, which are electrically connected to a corresponding subset of the first electrodes of the two-dimensional array; Bit lines, which are electrically connected to a corresponding subset of the second electrodes of the two-dimensional array; and A programming circuit connected to the bit lines and the word lines and configured to program the magnetoresistive memory device.

18. A method of operating a magnetoresistive memory device according to claim 1, the method comprising: In the first programming step, a first polarity programming voltage is applied to the first electrode relative to the second electrode to switch the state of the variable magnetic material layer from a non-magnetic state to a magnetic state; as well as In the second programming step, a second polarity programming voltage with the opposite polarity to the first polarity programming voltage is applied relative to the second electrode to switch the state of the variable magnetic material layer from the magnetic state to the non-magnetic state.

19. The method of claim 18, wherein: The first polarity programming voltage changes the polarization direction of the ferroelectric material layer from a first direction to a second direction, thereby changing the state of the variable magnetic material layer from the non-magnetic state to the magnetic state; and The second polarity programming voltage changes the polarization direction of the ferroelectric material layer from the second direction to the first direction, which causes the state of the variable magnetic material layer to change from the magnetic state to the non-magnetic state.

20. The method of claim 19, the method further comprising determining the state of the variable magnetic material layer by measuring the tunneling magnetoresistance of the variable magnetic tunnel junction.

21. A magnetoresistive memory device, the magnetoresistive memory device comprising: First electrode; Second electrode; and A layer stack, located between the first electrode and the second electrode, the layer stack including a multiferroic material layer and a variable magnetic tunnel junction, wherein the variable magnetic tunnel junction includes: Variable magnetic material layer; Reference magnetization layer; and An insulating barrier layer is located between the reference magnetization layer and the variable magnetic material layer; and The magnetoresistive memory device further includes a programming circuit configured to: A first programming pulse of first polarity is applied across the first and second electrodes to program the variable magnetic material layer into a magnetic state; and A second programming pulse of the opposite polarity to the first polarity is applied across the first electrode and the second electrode to program the variable magnetic material layer into a non-magnetic state.

22. The magnetoresistive memory device of claim 21, wherein the variable magnetic material layer contacts the multiferroic material layer and the insulating barrier layer.

23. The magnetoresistive memory device of claim 21, wherein the multiferroic material layer has a non-zero polarization coupled to the magnetization of the multiferroic material layer.

24. The magnetoresistive memory device according to claim 23, wherein: The magnetization of the multiferroic material layer has a bistable configuration, wherein the first magnetization direction and the second magnetization direction are stable directions for the magnetization of the multiferroic material layer; and The second magnetization direction is antiparallel to the first magnetization direction.

25. The magnetoresistive memory device according to claim 24, wherein: The multiferroic material layer is magnetically coupled to the variable magnetic material layer; and The change in the magnetization direction in the multiferroic material layer induces the transition between the magnetic state and the nonmagnetic state of the variable magnetomagnetic material layer.

26. The magnetoresistive memory device according to claim 25, wherein: The magnetization direction of the multiferroic material layer is coupled to the non-zero polarization direction of the multiferroic material layer; and The change in the direction of the non-zero polarization of the multiferroic material layer induces a change in the magnetization direction in the multiferroic material layer.

27. The magnetoresistive memory device according to claim 25, wherein: One of the first and second magnetization directions of the multiferroic material layer induces the magnetic state within the variable magnetic material layer, wherein the magnetic state includes a ferromagnetic state having a magnetization direction aligned with one of the first or second magnetization directions; and The first magnetization direction and the second magnetization direction of the multiferroic material layer induce the nonmagnetic state within the variable magnetic material layer.

28. The magnetoresistive memory device of claim 21, wherein the magnetic state of the variable magnetic material layer includes the ferromagnetic state of the variable magnetic material layer, and the nonmagnetic state of the variable magnetic material layer includes a paramagnetic state or an antimagnetic state.

29. The magnetoresistive memory device of claim 28, wherein the reference magnetization layer has a fixed magnetization direction oriented along the direction of the vertical component of the magnetization of the ferromagnetic state antiparallel to that of the variable magnetic material layer.

30. The magnetoresistive memory device according to claim 29, wherein: The variable magnetic tunnel junction has a first tunneling magnetic resistance when the variable magnetic material layer is in the non-magnetic state; and The variable magnetic tunnel junction has a second tunneling magnetic resistance greater than the first tunneling magnetic resistance when the variable magnetic material layer is in the magnetic state.

31. The magnetoresistive memory device of claim 21, further comprising a synthesized antiferromagnetic structure, the antiferromagnetic structure comprising: A reference magnetization layer, wherein the reference magnetization layer comprises a soft ferromagnetic layer; A fixed magnetization layer, which is spaced apart from the reference magnetization layer; and An antiferromagnetic coupling layer that antiferromagnetically couples the magnetization of the reference magnetization layer to the magnetization of the fixed magnetization layer.

32. The magnetoresistive memory device of claim 21, wherein the reference magnetization layer comprises a hard magnetic layer.

33. The magnetoresistive memory device of claim 21, wherein the multiferroic material layer comprises a material selected from the group consisting of: BiFeO3, h-YMnO3, BaNiF4, PbVO3, BiMnO3, LuFe2O4, HoMn2O5, h-HoMnO3, h-ScMnO3, h-ErMnO3, h-TmMnO3, h-YbMnO3, h-LuMnO3, K2SeO4, Cs2CdI4, TbMnO3, Ni3V2O8, MnWO4, CuO, ZnCr2Se4, LiCu2O2, or Ni3B7O. 13 I.

34. The magnetoresistive memory device of claim 21, wherein the variable magnetic material layer comprises a material selected from the group consisting of Co, FeRh alloy, EuSe alloy, CrO2, or LaSrMnO3.

35. The magnetoresistive memory device of claim 21, wherein the insulating barrier layer comprises a material selected from the group consisting of magnesium oxide, aluminum oxide, strontium titanate, or combinations thereof.

36. A magnetoresistive random access memory device, wherein the magnetoresistive random access memory device include: A two-dimensional array of an example of the magnetoresistive memory device according to claim 21; Word lines, which are electrically connected to a corresponding subset of the first electrodes of the two-dimensional array; Bit lines, which are electrically connected to a corresponding subset of the second electrodes of the two-dimensional array; and A programming circuit connected to the bit lines and the word lines and configured to program the magnetoresistive memory device.

37. A method of operating a magnetoresistive memory device according to claim 21, the method comprising: In the first programming step, a first polarity programming voltage is applied to the first electrode relative to the second electrode to switch the state of the variable magnetic material layer from a non-magnetic state to a magnetic state; as well as In the second programming step, a second polarity programming voltage with the opposite polarity to the first polarity programming voltage is applied relative to the second electrode to switch the state of the variable magnetic material layer from the magnetic state to the non-magnetic state.

38. The method of claim 37, wherein: The first polarity programming voltage changes the polarization direction of the multiferroic material layer from a first direction to a second direction, causing the state of the variable magnetic material layer to change from the non-magnetic state to the magnetic state; and The second polarity programming voltage changes the polarization direction of the multiferroic material layer from the second direction to the first direction, which causes the state of the variable magnetic material layer to change from the magnetic state to the non-magnetic state.

39. The method of claim 38, the method further comprising determining the state of the variable magnetic material layer by measuring the tunneling magnetoresistance of the variable magnetic tunnel junction.

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