A magnetoresistance high-entropy manganese oxide polycrystalline composite film with a heterostructure and a preparation method thereof

Abstract

This invention discloses a magnetoresistive high-entropy manganese oxide polycrystalline composite thin film with a heterostructure and its preparation method. The composite thin film includes a first high-entropy manganese oxide polycrystalline thin film layer (A layer), a simple oxide dispersed composite particle layer (B layer), and a second high-entropy manganese oxide polycrystalline thin film layer (A' layer) sequentially formed on a substrate; the general chemical formulas of A layer and A' layer are (H... x1 H x2 ...H xn MnO3, H is selected from La, Pr, Nd, Sm, Eu, Gd, Ca, Sr, 5rnO; the chemical formula of the B layer is (S y1 S y2 ...S ym ) a O b S is selected from the above element group, 1≤m≤3; there is a compositional gradient between layer A and layer A' in terms of the number of components and / or molar fraction. The preparation method includes substrate pretreatment, target preparation, and alternating deposition of layers A, B, and A'. This invention significantly improves the room temperature magnetoresistance effect and anisotropic magnetoresistance performance of the thin film through the synergistic regulation of heterostructure and compositional gradient, and broadens the operating temperature window, making it suitable for high-precision magnetic sensor devices.

Description

Technical Field

[0001] This invention belongs to the field of thin film materials, specifically relating to a magnetoresistive high-entropy manganese oxide polycrystalline composite thin film with a dispersed anisotropic arrangement of heterogeneous structures and a composition gradient, and its preparation method. Background Technology

[0002] With the rapid development of microelectronics, magnetic sensing, and spintronics, the performance requirements for magnetoresistive functional thin films are constantly increasing. High-entropy manganese oxide thin films, with their core advantages such as high-entropy effect and lattice distortion effect, exhibit characteristics that surpass those of traditional doped oxides in terms of structural controllability and functional tunability, providing a new approach for breakthroughs in the performance of magnetoresistive thin films.

[0003] However, existing research on the preparation of magnetoresistive high-entropy manganese oxide thin films mostly adopts a single-layer structure design, which has the following significant shortcomings: First, the thin film structure is simple and does not introduce a dispersed heterogeneous composite phase. It is impossible to effectively control the carrier transport behavior using the heterostructure interface, resulting in weak magnetoresistive effect of the thin film at room temperature and low magnetic field, poor anisotropic magnetoresistive performance, and difficulty in meeting the requirements of high-precision magnetic sensing and magnetic storage devices. Second, the composition design of the high-entropy oxide layer lacks flexibility, generally using fixed component types and contents, lacking control over the number of components and composition gradients in the film growth direction. It is impossible to optimize the microstructure and electromagnetic properties through multi-element synergy and interface effects, resulting in the inability to flexibly control the metal-insulator phase transition temperature of the thin film, a narrow operating temperature window, and limited functional adjustability. Third, the limitations of the above-mentioned structure and composition design further make it difficult to guarantee the service stability of the thin film.

[0004] Therefore, there is an urgent need to develop a novel composite thin film with a new structure and composition design and its preparation method to solve the problems of weak magnetoresistance effect, poor temperature adaptability and insufficient performance adjustability in the existing technology. Summary of the Invention

[0005] The purpose of this invention is to provide a high-entropy magnetoresistive manganese oxide polycrystalline composite thin film with heterogeneous structure and composition gradient, and its preparation method, so as to solve the technical problems of weak magnetoresistive effect, insufficient flexibility in composition design, and narrow temperature control window of metal-insulator phase transition in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A magnetoresistive high-entropy manganese oxide polycrystalline composite thin film with a heterostructure and its preparation method thereof, comprising sequentially forming the following on a substrate: First high-entropy manganese oxide polycrystalline thin film layer (A layer); Simple oxide dispersed composite particle layer (B layer); Second high-entropy manganese oxide polycrystalline thin film layer (A' layer); The general chemical formulas of layer A and layer A' are respectively (H) x1 H x2 ...H xn MnO3 and (H') x1 H' x2 ...H' xn’ MnO3, wherein H and H' are each independently selected from the group containing La, Pr, Nd, Sm, Eu, Gd, Ca, and Sr, and H x1 ~H xn and H' x1 ~H' xn’ All are distinct, 5≤n≤8, 5≤n'≤8, and the mole fractions xi and x'i of each element satisfy the following conditions: =1 and =1; La, Pr, Nd, Sm, Eu, and Gd are rare earth elements, and Ca and S are alkaline earth elements. The general chemical formula of the B layer is (S y1 S y2 ...S ym ) a O b , among which, S y1 ~S ym Let S be a set of distinct elements, selected from the group containing La, Pr, Nd, Sm, Eu, Gd, Ca, and Sr, where 1 ≤ m ≤ 3, and the mole fraction yi of each element satisfies the following condition. =1; A composition gradient exists between layers A and A', which is achieved by the following: the quantities of n and n' are different, and / or, for the same element, its mole fraction x i With x' i They are not the same.

[0007] Further optimization involves layer A and / or layer A' being a multi-film layer structure composed of multiple sub-film layers. This multi-film layer structure contains a composition gradient, achieved through the following methods: the number of high-entropy components n in adjacent sub-film layers are different, and / or, for the same element, its mole fraction x... i They are not the same.

[0008] Further optimization involves a multi-film layer structure (A-multi) composed of multiple sub-film layers. When layer A or A' is a multi-film layer structure, a compositional gradient exists between the multi-film layer structure A-multi and the single film layer A. This gradient is achieved by ensuring that the number n of high-entropy components in the sub-film layer closest to layer B in the multi-film layer structure A-multi is different from that in the adjacent single film layer A, and / or that the mole fraction x of the same elements is different. i They are not the same.

[0009] Further optimization is achieved when both layers A and A' are multi-film layer structures composed of multiple sub-film layers. A compositional gradient exists between the two multi-film layer structures, achieved by ensuring that the number n of high-entropy components in the sub-film layers closest to layer B in both structures are different, and / or that the mole fraction x of the same elements is different. i They are not the same.

[0010] Further optimization is possible, and the composition of layer B can be any one or a combination of the following: ① Simple oxides composed of a single element, i.e., m=1; ② Simple oxides composed of multiple elements, i.e., m=2 or 3; The combination specifically refers to: a simple oxide composed of multiple single elements, a simple oxide composed of multiple elements, or a combination of a single element and a simple oxide composed of multiple elements.

[0011] On the other hand, the present invention also provides a method for preparing the above-mentioned magnetoresistance high-entropy manganese oxide polycrystalline composite thin film with heterostructure, comprising the following steps: Step 1: Substrate pretreatment; Step 2, target preparation: high-entropy manganese oxide target and simple oxide target are prepared respectively; Step 3: The first high-entropy manganese oxide polycrystalline thin film layer (A layer) is deposited on the substrate using physical sputtering. Step four: Using physical sputtering, a composite particle layer (layer B) of simple oxide dispersed and anisotropically arranged particles is deposited on layer A. Step 5: Using physical sputtering, a second high-entropy manganese oxide polycrystalline thin film layer (A' layer) is deposited on the B layer.

[0012] Further optimization is achieved by the following process conditions for depositing layer A or layer A' in steps three and five: First, the high-entropy manganese oxide target material undergoes surface pre-deposition treatment, during which oxygen is introduced to maintain an oxygen pressure of 1.33 × 10⁻⁶. -5 Pa~1.33 Pa, pre-deposition pulse number 100 pulse~500 pulse, energy density 0.50 J / cm³ 2 ~1.00 J / cm 2 ; Then, formal deposition and growth took place, during which flowing oxygen was introduced to maintain an oxygen pressure of 1.33 Pa to 1.9 × 10⁻⁶ Pa. 4 Pa, deposition pulse number of 200 pulses to 30,000 pulses, energy density of 1.00 J / cm³ 2 ~2.00 J / cm 2The substrate heating temperature is 200 ℃~800 ℃.

[0013] Further optimization is achieved by setting the deposition process conditions for layer B in step four as follows: First, a surface pre-deposition treatment was performed on the simple oxide target material, during which oxygen was introduced to maintain an oxygen pressure of 1.33 × 10⁻⁶. -5 Pa~1.33 Pa, pre-deposition pulse number 100 pulse~500 pulse, energy density 0.50 J / cm³ 2 ~1.00 J / cm 2 ; Then, formal deposition and growth took place, during which flowing oxygen was introduced to maintain an oxygen pressure of 1.33 Pa to 1.9 × 10⁻⁶ Pa. 4 Pa, deposition pulse number from 1 to 1000 pulses, energy density of 0.05 J / cm³ 2 ~1.00 J / cm 2 The substrate heating temperature is 200℃~800℃.

[0014] Further optimization involves using pulsed laser deposition or magnetron sputtering as the physical sputtering method.

[0015] Further optimization is achieved by selecting SiN as the substrate in step one. δ One of Si or mica; the SiN δ The substrate thickness is 40 μm to 10000 μm, and δ = 1.00 to 1.33; the Si substrate thickness is 20 μm to 10000 μm, and the crystal plane index is [missing value]. <100> , <111> or <110> The type is P-type or N-type; the mica substrate is natural muscovite or fluorinated mica, with a thickness of 100μm~10000 μm and a surface roughness of ≤0.5 nm.

[0016] Further optimization involves employing an in-situ interface pretreatment process for the substrate pretreatment described in step one, which includes the following steps: (1) Provide a substrate and wipe the surface of the substrate with dilute hydrofluoric acid with a concentration of 0.5%~2% for 3 min~10 min; (2) Place the wiped substrate into the deposition chamber and evacuate the chamber to a background vacuum of ≤1×10⁻ 6 Torr; (3) High-purity argon gas is introduced into the cavity as a protective atmosphere, and the substrate is heated to 100 ℃, 300 ℃ and 500 ℃ in sequence at a heating rate of 5 ℃ / min to 50 ℃ / min, and each temperature step is held for 20 min to 30 min. (4) Cool the substrate to room temperature at a cooling rate of 5 ℃ / min~30 ℃ / min, stop the argon gas supply, and evacuate the cavity again to a vacuum of ≤1×10⁻ 6 Torr, to obtain the substrate after interface pretreatment.

[0017] Further optimization involves the target preparation in step two, employing a sol-gel method combined with a stepwise sintering process, including the following steps: (1) Weigh the required metal nitrate according to the stoichiometric ratio and dissolve it in a mixed solvent of water and methanol to form a cationic mixed solution; (2) Citric acid as a chelating agent and ethylene glycol as a dispersant were added sequentially to the mixed solution, and the mixture was heated and evaporated to obtain a gel; (3) After drying and grinding the gel, it is sintered once in an oxygen atmosphere with a slight positive pressure of +5 Pa to +30 Pa. The sintering temperature is 400 ℃ to 700 ℃ and the sintering time is 2 h to 16 h. (4) Press the sintered powder into shape and sinter it in an oxygen atmosphere with a slight positive pressure of +5 Pa to +30 Pa. The sintering temperature is 1000 ℃ to 1700 ℃ and the sintering time is 10 h to 24 h to obtain oxide target material.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention innovatively constructs a sandwich heterostructure consisting of a "high-entropy manganese oxide polycrystalline thin film layer (A layer) / a simple oxide dispersed composite particle layer (B layer) / a high-entropy manganese oxide polycrystalline thin film layer (A' layer)". By introducing a dispersed and anisotropically arranged simple oxide particle phase, a large number of controllable heterostructure interfaces are formed inside the thin film. These interfaces can effectively regulate the carrier scattering degree and spin-related transport process, significantly enhance the magnetoresistance effect and anisotropic magnetoresistance at low field and room temperature, improve the magnetoresistance value and broaden the operating response temperature window to meet the application requirements of high-precision magnetic sensors and spintronic devices.

[0019] (2) This invention introduces a multi-dimensional composition gradient in the alternating composite structure, including gradient changes in the number and molar fraction of components between single layers, within multiple layers, and between them. This flexible and precise composition gradient design breaks through the performance bottleneck of traditional fixed-component thin films, and realizes continuous control of the microstructure of the thin film, carrier concentration, and phase competition. This significantly broadens the metal-insulator phase transition temperature window, greatly improves the functional tunability of the thin film, and provides a feasible path for customized design of thin film performance for different application scenarios.

[0020] (3) Through the synergistic effect of heterostructure design and component gradient regulation, this invention optimizes the lattice matching and stress distribution of the thin film. Combined with the inherent hysteresis diffusion effect of the high-entropy system, it significantly improves the thermal stability, phase stability and interfacial bonding of the thin film, effectively avoids defects such as cracking and peeling of the thin film, and ensures the reliability and stability of the device during long-term service. Attached Figure Description

[0021] To more clearly illustrate the technical solutions involved in the embodiments of the present invention or the prior art, the accompanying drawings included in the description of the embodiments or the prior art will be briefly introduced below. It should be noted that these drawings only show some specific embodiments recorded in the present invention and do not cover all possible implementations.

[0022] Figure 1 The image shows the X-ray diffraction pattern of the composite thin film obtained in Example 1. Figure 2 This is a scanning electron microscope image of the alternating composite structure thin film of multilayer A / single layer B / single layer A in Example 3; Figure 3 This is a scanning electron microscope image of the alternating composite structure of multilayer A / single-layer B / multilayer A in Example 4; Figure 4 An atomic force microscope image of the 8-component high-entropy manganese oxide thin film of Example 5; Figure 5 This is an atomic force microscope image of the composite thin film containing a B layer of various simple oxide combinations in Example 6; Figure 6 The graph shows the gradient variation of the number of components in the multi-film layer A in Example 7, and the thin film magnetoresistance performance of the multi-element simple oxide layer B. Figure 7 This is an anisotropic magnetoresistance performance diagram of a composite thin film with a symmetrical compositional gradient deposited on a Si substrate in Example 8. Detailed Embodiments The technical solution of the present invention will now be described in detail and comprehensively. It should be noted that the embodiments described are only a part of the present invention and do not cover all embodiments. Furthermore, all other embodiments that can be obtained by those skilled in the art based on the embodiments provided by the present invention without creative effort should also fall within the protection scope of the present invention. In the following embodiments, unless otherwise specified, the instruments and materials used are commercially available.

[0023] Example 1: In this example, a magnetoresistive high-entropy manganese oxide polycrystalline composite film with an alternating A / B / A' composite structure was prepared, wherein the number of high-entropy components in the A layer and the A' layer is the same, but the types of rare earth elements vary.

[0024] Layer A is designed as (La) 0.25Pr 0.25 Nd 0.25 Sm 0.25 ) 0.7 Ca 0.3 MnO3, i.e., the number of high-entropy components n=5, the rare earth components are La, Pr, Nd, and Sm, the alkaline earth component is Ca, and the rare earth elements are in equal molar ratios.

[0025] The A' layer composition is designed as (La) 0.25 Pr 0.25 Nd 0.25 Eu 0.25 ) 0.7 Ca 0.3 MnO3, i.e., the number of high-entropy components n=5, the rare earth components are La, Pr, Nd, Eu, and the alkaline earth component is Ca, with each rare earth element in an equal molar ratio.

[0026] The B layer composition is designed as La2O3, i.e., m=1, and the rare earth element selected is La.

[0027] This embodiment describes a method for preparing a magnetoresistive high-entropy manganese oxide polycrystalline composite thin film with a heterostructure, comprising the following steps: Step 1: Substrate pretreatment. SiN is selected. δ The substrate has a δ = 1.10, a thickness of 200 μm, and a surface area of ​​1 cm². 2 The substrate is square. Using lint-free paper soaked in a 1% dilute hydrofluoric acid solution, gently and evenly wipe the entire surface of the substrate for 5 minutes. Immediately after wiping, place the substrate into the pulsed laser deposition cavity, close the cavity door, and initiate the vacuum process to achieve a base vacuum of 8 × 10⁻⁶. -7 Torr. High-purity argon gas (99.999%) was continuously introduced into the chamber as a protective atmosphere. The substrate was gradually heated to 100 °C at a heating rate of 30 °C / min and held for 25 min; then heated to 300 °C at the same rate and held for 25 min; finally, heated to 500 °C at a heating rate of 20 °C / min and held for 20 min. After the holding period, the substrate temperature was gradually reduced to room temperature at a cooling rate of 15 °C / min. The high-purity argon gas supply was stopped, and the chamber was evacuated again to a vacuum of 5 × 10⁻⁵. -7 Torr, to obtain substrate I after interface pretreatment.

[0028] Step 2: Target preparation.

[0029] High-entropy manganese oxide target material A is designed according to the composition (La) 0.25 Pr 0.25 Nd 0.25 Sm 0.25 ) 0.7 Ca 0.3MnO3, i.e., the number of high-entropy components n=5, the rare earth components are La, Pr, Nd, and Sm, the alkaline earth component is Ca, and the rare earth elements are in equal molar ratios.

[0030] The high-entropy manganese oxide target A' is designed according to the composition (La) 0.25 Pr 0.25 Nd 0.25 Eu 0.25 0.7Ca 0.3 MnO3, i.e., the number of high-entropy components n=5, the rare earth components are La, Pr, Nd, Eu, and the alkaline earth component is Ca.

[0031] Lanthanum nitrate, praseodymium nitrate, neodymium nitrate, samarium nitrate (A' being europium nitrate), calcium nitrate, and manganese nitrate were accurately weighed according to stoichiometric ratios and added to a mixture of deionized water and methanol (volume ratio 1:1) and stirred until completely dissolved. Citric acid was added to the solution as a chelating agent, with a molar ratio of citric acid to total metal ions of 1.5:1; ethylene glycol was then added as a dispersant, with the amount of ethylene glycol being 30% of the mass of citric acid. The mixture was placed on a magnetically heated stirring table and continuously stirred at 80 °C to evaporate and form a wet gel. The wet gel was then transferred to an oven and dried at 120 °C for 20 h to obtain a dry gel. After grinding the dry gel for 48 h, it was placed in a tube furnace, with flowing oxygen introduced and a slight positive pressure of +15 Pa maintained inside the furnace. The temperature was increased to 550 °C at a rate of 5 °C / min and held at that temperature for 10 h for a first sintering. The sintered powder was pressed into shape by cold isostatic pressing at 150 MPa for 20 min. It was then heated to 1350 ℃ at a rate of 3 ℃ / min in a slightly positive pressure + 20 Pa oxygen atmosphere and held for 20 h for secondary sintering. The powder was then cooled in the furnace to obtain target material A and target material A'.

[0032] Simple oxide target B uses La₂O₃ as its component, i.e., m=1, and La is selected as the rare earth element. Lanthanum nitrate is weighed according to the stoichiometric ratio, and the La₂O₃ target is prepared using the same sol-gel and stepwise sintering process as described above.

[0033] Step 3: Deposit Layer A. The target material A and substrate I are placed into the pulsed laser deposition cavity, and their positions are adjusted to correspond. A KrF excimer laser (wavelength 248 nm) is used. First, a pre-deposition treatment is performed on the surface of the A1 target material: oxygen is introduced to achieve an oxygen pressure of 1.33 × 10⁻⁶. -3 Pa, pulse number 300 pulses, energy density 0.80 J / cm³ 2 After pre-deposition, the oxygen pressure was adjusted to 10 Pa, the pulse number to 5000 pulses, and the energy density to 1.50 J / cm³. 2The substrate is heated to 650 ℃. The laser beam bombards the center of the A1 target to generate a high-entropy manganese oxide plasma plume, which falls freely and uniformly onto the surface of substrate I to deposit and form a high-entropy manganese oxide polycrystalline thin film layer.

[0034] Step 4: Deposit Layer B. Switch to La2O3 target material and first perform pre-deposition treatment: oxygen pressure 1.33 × 10⁻³ Pa, pulse number 300 pulses, energy density 0.80 J / cm². After pre-deposition, adjust the oxygen pressure to 5 Pa, pulse number 200 pulses, energy density 0.20 J / cm², and substrate heating temperature to 650 ℃ to form a La2O3 dispersed composite particle layer on the surface of Layer A1.

[0035] Step 5: Deposit layer A'. Switch to target A' and perform pre-deposition as in step 3. The formal deposition parameters are: oxygen pressure 10 Pa, pulse number 5000 pulses, energy density 1.50 J / cme, substrate heating temperature 650 °C. A high-entropy manganese oxide polycrystalline thin film layer A' is deposited on layer B.

[0036] The X-ray diffraction pattern of the composite thin film obtained in this embodiment is as follows: Figure 1 As shown.

[0037] The A' layer of the composite film obtained in this embodiment is (La 0.25 Pr 0.25 Nd 0.25 Sm 0.25 ) 0.7 Ca 0.3 MnO3, layer B consists of La2O3 dispersed particles, and layer A' consists of (La) 0.25 Pr 0.25 Nd 0.25 Eu 0.25 0.7Ca 0.3 MnO3. There is a gradient of constituent element types between the A layer and the A' layer: the rare earth constituents in the A layer are La, Pr, Nd, and Sm, while Sm is replaced by Eu in the A' layer, thus achieving a gradient change in the types of rare earth elements.

[0038] Example 2: In this example, an alternating composite structure of single-layer A / single-layer B / single-layer A' was prepared. The types of high-entropy components in layer A and layer A' are exactly the same, but the mole fractions vary.

[0039] Layer A is designed as (La) 0.2 Pr 0.2 Nd 0.2 Sm 0.2 Ca 0.1 Sr 0.1MnO3, with a high-entropy component number of n=6, and the rare earth / alkaline earth elements are La, Pr, Nd, Sm, Ca, and Sr, respectively.

[0040] The A' layer composition is designed as (La) 0.2 Pr 0.15 Nd 0.15 Sm 0.15 Ca 0.125 Sr 0.125 MnO3 has the same number of high-entropy components as A, n=6.

[0041] The B layer composition was designed as La2O3 (m=1).

[0042] This embodiment describes a method for preparing a magnetoresistive high-entropy manganese oxide polycrystalline composite thin film with a heterostructure, comprising the following steps: Step 1: Substrate pretreatment. Same as Example 1.

[0043] Step 2: Target preparation.

[0044] The high-entropy manganese oxide target material component A is designed as (La 0.2 Pr 0.2 Nd 0.2 Sm 0.2 Ca 0.1 Sr 0.1 MnO3, with a high-entropy component number of n=6, and the rare earth / alkaline earth elements are La, Pr, Nd, Sm, Ca, and Sr, respectively.

[0045] The high-entropy manganese oxide target A' is designed with the following composition: (La 0.2 Pr 0.15 Nd 0.15 Sm 0.15 Ca 0.125 Sr 0.125 MnO3 has the same number of high-entropy components as A, n=6.

[0046] The simple oxide target B is La2O3 (m=1).

[0047] The target preparation process is the same as in Example 1.

[0048] Step 3: Deposit Layer A. The target material A and substrate I are placed into the pulsed laser deposition cavity, and their positions are adjusted to correspond. A KrF excimer laser (wavelength 248 nm) is used. First, a pre-deposition treatment is performed on the surface of the target material A: oxygen is introduced to achieve an oxygen pressure of 1.33 × 10⁻⁶. -3 Pa, pulse number 800 pulses, energy density 0.80 J / cm³ 2After pre-deposition, the oxygen pressure was adjusted to 15 Pa, the pulse number to 8000 pulses, and the energy density to 1.60 J / cm³. 2 The substrate is heated to 700 ℃. A laser beam bombards the center of target A to generate a high-entropy manganese oxide plasma plume, which falls freely and uniformly onto the surface of substrate I, depositing a high-entropy manganese oxide polycrystalline thin film layer A.

[0049] Step 4: Deposit Layer B. Switch to La2O3 target material and perform pre-deposition treatment: oxygen pressure 1.33 × 10⁻³ Pa, pulse number 300 pulses, energy density 0.80 J / cm². After pre-deposition, adjust the oxygen pressure to 8 Pa, pulse number 150 pulses, energy density 0.15 J / cm², and substrate heating temperature to 500 ℃ to form a La2O3 dispersed composite particle layer on the surface of layer A.

[0050] Step 5: Deposit layer A'. Switch to target A' and perform pre-deposition as in step 3. The formal deposition parameters are: oxygen pressure 15 Pa, pulse number 8000 pulses, energy density 1.60 J / cme, substrate heating temperature 700 °C. A high-entropy manganese oxide polycrystalline thin film layer A' is deposited on layer B.

[0051] In this embodiment, the high-entropy component elements of layers A and A' are exactly the same, namely six elements: La, Pr, Nd, Sm, Ca, and Sr. However, the mole fractions of Pr, Nd, and Sm change from 0.2 to 0.15, respectively, the mole fractions of Ca and Sr change from 0.1 to 0.125, respectively, and the mole fraction of La remains unchanged, thus achieving gradient control of mole fraction under the same component types.

[0052] Example 3: This example employs an alternating composite structure of multilayer A / single-layer B / single-layer A', with a compositional gradient of alkaline earth elements and rare earth elements existing between multilayer A and single-layer A'. The composition design is as follows: Multilayer A consists of 3 sublayers, all designed with a composition of (La). 0.20 Pr 0.20 Nd 0.20 Sm 0.20 Gd 0.20 ) 0.8 Ca 0.2 MnO3.

[0053] The single-layer A' component is designed as (La 0.20 Pr 0.20 Nd 0.20 Eu 0.20 Gd 0.20 ) 0.8 Sr 0.2 MnO3.

[0054] The B-layer composition is designed as (La) 0.5 Nd 0.5 )2O3, i.e., m=2.

[0055] The specific preparation steps are as follows: Step 1: Substrate pretreatment.

[0056] A p-type Si(100) substrate with a resistivity of 1~10 Ω·cm, a thickness of 400 μm, and a circular shape with an area of ​​0.25 cm² was selected. The substrate surface was wiped with 2% dilute hydrofluoric acid using lint-free paper for 3 min. The temperature was increased in steps at a rate of 50 °C / min, with temperature steps of 100 °C for 30 min, 300 °C for 30 min, and 500 °C for 25 min; the cooling rate was 30 °C / min. The remaining pretreatment procedures were the same as in Example 1.

[0057] Step 2: Target preparation.

[0058] The composition of target material A is designed to be (La). 0.20 Pr 0.20 Nd 0.20 Sm 0.20 Gd 0.20 ) 0.8 Ca 0.2 MnO3.

[0059] The composition of the A' target material is designed as (La) 0.20 Pr 0.20 Nd 0.20 Eu 0.20 Gd 0.20 ) 0.8 Sr 0.2 MnO3.

[0060] B. Simple oxide target material is (La) 0.5 Nd 0.5 )2O3, i.e., m=2, the rare earth elements selected are La and Nd.

[0061] The target preparation process is the same as in Example 1, except that Sr in the A' target is introduced in the form of strontium nitrate.

[0062] Step 3: Deposit multilayer A. Multilayer A consists of three sublayers stacked sequentially, as detailed below: Depositing the first sublayer (A-1, bottom layer): Adjust the target position so that target A is aligned with substrate I. First, pre-deposit treatment is performed on the target surface: oxygen is introduced to achieve an oxygen pressure of 1.33 × 10⁻⁶. -3Pa, pulse number 300 pulses, energy density 0.80 J / cm². After pre-deposition, the oxygen pressure was adjusted to 20 Pa, pulse number 2000 pulses, energy density 1.40 J / cm², substrate heating temperature 600 ℃, and plasma plume generated by laser beam bombardment of the target center, depositing a (La) composition on the surface of substrate I. 0.20 Pr 0.20 Nd 0.20 Sm 0.20 Gd 0.20 ) 0.8 Ca 0.2 The first sub-film layer of MnO3.

[0063] Depositing the second sub-film layer (A-2, middle layer): The position of target A remains unchanged. Pre-deposition parameters are the same as for the first sub-film layer. After pre-deposition, oxygen pressure is 20 Pa, pulse number is 2000 pulses, energy density is 1.40 J / cm², and substrate heating temperature is 600℃. A film with the composition (La) is deposited on the surface of the first sub-film layer. 0.20 Pr 0.20 Nd 0.20 Sm 0.20 Gd 0.20 ) 0.8 Ca 0.2 The second sub-film layer of MnO3.

[0064] Depositing the third sub-film layer (A-3, top layer): The target position of layer A remains unchanged. Pre-deposition parameters are the same as for the first sub-film layer. After pre-deposition, oxygen pressure is 20 Pa, pulse number is 2000 pulses, energy density is 1.40 J / cm², and substrate heating temperature is 600℃. A film with the composition (La) is deposited on the surface of the second sub-film layer. 0.20 Pr 0.20 Nd 0.20 Sm 0.20 Gd 0.20 ) 0.8 Ca 0.2 The third sub-film layer of MnO3.

[0065] This results in a multilayer A composed of three sublayers, with a total thickness approximately three times that of a single layer A.

[0066] Step 4: Deposit layer B.

[0067] Oxygen pressure 10 Pa, pulse number 500 pulses, energy density 0.30 J / cm², substrate temperature 600 ℃.

[0068] Step 5: Deposit a single film layer A'.

[0069] Oxygen pressure 20 Pa, pulse number 6000 pulses, energy density 1.40 J / cm², substrate temperature 600 ℃.

[0070] The topmost layer (closest to layer B) of the multilayer A consists of La, Pr, Nd, Sm, Gd, and Ca, while the single-layer A' consists of La, Pr, Nd, Eu, Gd, and Sr. There is a two-dimensional compositional gradient between them: a substitution gradient of alkaline earth elements Ca→Sr, and a substitution gradient of rare earth elements Sm→Eu. The scanning electron microscope image of the alternating multilayer A / single-layer B / single-layer A composite thin film prepared in this embodiment is shown below. Figure 2 As shown.

[0071] Example 4: The structure of this example is a multilayer A / single layer B / multilayer A'. There are compositional gradients between the sublayers within multilayer A and A' and between the two multilayers.

[0072] Multilayer A consists of 3 sublayers. A-1 (bottom layer): (La) 0.30 Pr 0.20 Nd 0.20 Sm 0.15 Gd 0.15 ) 0.75 Ca 0.25 MnO3, n=6 A-2 (Middle Layer): (La) 0.25 Pr 0.20 Nd 0.20 Sm 0.15 Gd 0.20 ) 0.75 Ca 0.25 MnO3, n=6 A-3 (Top Floor): (La) 0.20 Pr 0.20 Nd 0.20 Sm 0.20 Gd 0.20 ) 0.75 Ca 0.25 MnO3, n=6 The multilayer A' consists of two sublayers: A'-1 (bottom layer): (La) 0.20 Pr 0.20 Nd 0.20 Eu 0.20 Gd 0.20 ) 0.80 Sr 0.20 MnO3, n=6 A'-2 (Top Layer): (La) 0.25 Pr 0.20 Nd 0.15 Eu0.15 Gd 0.25 ) 0.85 Sr 0.15 MnO3, n=6 The monolayer B is La2O3 (m=1). The specific preparation steps are as follows: Step 1: Substrate Pretreatment. A fluorocrystalline mica substrate with a thickness of 500 μm, a surface roughness of 0.3 nm, and an area of ​​4 cm² was selected. The surface was gently wiped for 10 min with a 0.5% dilute hydrofluoric acid solution using a lint-free paper towel. The temperature was increased in steps at a rate of 5 °C / min, with each temperature step held for 30 min; the cooling rate was 5 °C / min. The rest was the same as in Example 1.

[0073] Step 2: Target preparation.

[0074] The high-entropy manganese oxide target material component A is designed as (La 0.30 Pr 0.20 Nd 0.20 Sm 0.15 Gd 0.15 ) 0.75 Ca 0.25 MnO3, n=6 The high-entropy manganese oxide target A' is designed with the following composition: (La 0.20 Pr 0.20 Nd 0.20 Eu 0.20 Gd 0.20 ) 0.80 Sr 0.20 MnO3, n=6 The simple oxide target material is La2O3 (m=1).

[0075] The target preparation process is the same as in Example 1.

[0076] Steps 3 to 5: The deposition of the multi-layer film is the same as in Example 3, except that the deposition temperature is 550 ℃, the oxygen pressure is 25 Pa, and the energy density is 1.80 J / cm². Each sub-layer is deposited sequentially, with a pulse count of 3000 pulses for each layer. Layer B is deposited with 80 pulses and an energy density of 0.10 J / cm².

[0077] This embodiment achieves a three-dimensional compositional gradient: La decreases from 0.30 to 0.25 to 0.20 and Gd increases from 0.15 to 0.20 to 0.20 within multilayer A; La and Gd increase while Nd and Eu decrease within multilayer A'; and alkaline earth element Ca→Sr substitution and rare earth element Sm→Eu substitution occur between the top layer A and the bottom layer A'. The resulting film achieves an AMR value of 4.8% at room temperature and a 0.5 T magnetic field. Scanning electron microscopy images of the alternating multilayer A / single-layer B / multilayer A composite thin film prepared in this embodiment are shown below. Figure 3 As shown.

[0078] Example 5: This example is an 8-component high-entropy manganese oxide thin film with a gradient in the number of components. In this embodiment, layer A adopts an 8-component design, and layer A' adopts a 5-component design, with a gradient change in the number of components n between A and A'.

[0079] This embodiment describes a method for preparing a magnetoresistive high-entropy manganese oxide polycrystalline composite thin film with a heterostructure, comprising the following steps: Step 1: Substrate pretreatment. An N-type Si(110) substrate with a thickness of 500 μm and a surface area of ​​2 cm² was selected. The pretreatment procedure was the same as in Example 1.

[0080] Step 2: Target preparation.

[0081] Component A is designed as (La) 0.15 Pr 0.15 Nd 0.15 Sm 0.15 Eu 0.10 Gd 0.10 Ca 0.1 0Sr 0.10 MnO3 has a high-entropy component number of n=8, containing all 8 optional elements.

[0082] Component A' is designed as (La) 0.25 Pr 0.25 Nd 0.25 Sm 0.25 ) 0.7 Ca 0.3 MnO3, number of high-entropy components n=5.

[0083] The simple oxide target material is La2O3 (m=1).

[0084] Target material A was sintered under a slightly positive pressure of +20 Pa at 650 ℃ for 16 h, followed by a second sintering under a slightly positive pressure of +25 Pa at 1700 ℃ for 24 h, with a heating rate of 1 ℃ / min. The remaining target material preparation processes were the same as in Example 1.

[0085] Steps 3 to 5: Deposit layer A with an oxygen pressure of 12 Pa, 10,000 pulses, an energy density of 1.80 J / cm², and a substrate temperature of 750 ℃. Deposit layer B with an oxygen pressure of 6 Pa, 300 pulses, an energy density of 0.25 J / cm², and a substrate temperature of 750 ℃. The deposition parameters for layer A' are the same as for layer A.

[0086] This embodiment achieves a gradient change in the number of high-entropy components n from 8 to 5. The 8-component A layer fully utilizes the high-entropy effect to enhance thermal stability, while the 5-component A' layer optimizes magnetoresistance performance. Together, they broaden the operating temperature window and adjustable performance range of the thin film. An atomic force microscopy image of the 8-component high-entropy manganese oxide thin film prepared in this embodiment is shown below. Figure 4 As shown.

[0087] Example 6: In this example, layer B is composed of a combination of various simple oxides, further enriching the types of heterogeneous interfaces.

[0088] This embodiment describes a method for preparing a magnetoresistive high-entropy manganese oxide polycrystalline composite thin film with a heterostructure, comprising the following steps: Step 1: Substrate pretreatment. A SiNδ substrate with δ=1.20, a thickness of 1000 μm, and an area of ​​9 cm² was selected. The pretreatment procedure was the same as in Example 1.

[0089] Step 2: Target preparation.

[0090] Both layer A and layer A' are designed with (La) as the component. 0.2 Pr 0.2 Nd 0.2 Sm 0.2 Ca 0.1 Sr 0.1 MnO3 (n=6).

[0091] Simple oxide targets include three types: La₂O₃ (m=1), Nd₂O₃ (m=1), and (La₂O₃)₂O₃. 0.5 Nd 0.5 )2O3 (m=2).

[0092] The target preparation process is the same as in Example 1.

[0093] Step 3: Deposit layer A. Oxygen pressure 15 Pa, pulse number 8000 pulses, energy density 1.50 J / cm², substrate temperature 680 ℃.

[0094] Step 4: Deposit Layer B. Three targets were used sequentially to deposit: La₂O₃ particle layer (80 pulses, 0.15 J / cm²); Nd₂O₃ particle layer (80 pulses, 0.15 J / cm²); (La 0.5Nd 0.5 A layer of O2 particles (100 pulses, energy density 0.20 J / cm²) was formed. The oxygen pressure was 8 Pa, and the substrate temperature was 680 °C. A B layer consisting of a dispersed arrangement of various simple oxide combinations was created.

[0095] Step 5: Deposit layer A'. Parameters are the same as in step 3.

[0096] In this embodiment, layer B contains three different simple oxides, forming a more diverse heterogeneous interface. The synergistic effect of the multiple simple oxides further enhances the interface scattering effect, resulting in a room-temperature AMR value that is approximately 25% higher than that of a single La2O3 particle layer. An atomic force microscopy image of the composite film containing a layer B with multiple simple oxide combinations prepared in this embodiment is shown below. Figure 5 As shown.

[0097] Example 7: In this example, the number of components n in the sub-films inside the multi-film layer A gradually changes, and the B layer uses a multi-element simple oxide.

[0098] This embodiment describes a method for preparing a magnetoresistive high-entropy manganese oxide polycrystalline composite thin film with a heterostructure, comprising the following steps: Step 1: Substrate Pretreatment. A natural muscovite substrate with a thickness of 800 μm, a surface roughness of 0.4 nm, and a size of 6 cm² was selected. The pretreatment procedure was the same as in Example 4.

[0099] Step 2: Target preparation.

[0100] Multilayer A consists of 4 sublayers, with the number of components n increasing sequentially: A-1: (La 0.25 Pr 0.25 Nd 0.25 Sm 0.25 ) 0.8 Ca 0.2 MnO3 (n=5) A-2: (La 0.20 Pr 0.20 Nd 0.20 Sm 0.20 Gd 0.20 ) 0.8 Ca 0.2 MnO3 (n=6) A-3: (La 0.15 Pr 0.15 Nd 0.15 Sm 0.15 Eu 0.10 Gd 0.10 Ca 0.10 Sr 0.10 MnO3 (n=8) A' layer: (La0.25 Pr 0.25 Nd 0.25 Sm 0.25 ) 0.7 Ca 0.3 MnO3 (n=5).

[0101] Simple oxide target material is (Sm 0.5 Gd 0.5 )2O3 (m=2).

[0102] The target preparation process is the same as in Example 1.

[0103] Steps 3 to 5: The deposition of the multi-layer film is the same as in Example 3, except that the deposition temperature is 600 ℃, the oxygen pressure is 20 Pa, the energy density is 1.60 J / cm², and the number of pulses for each sub-layer is 2000 pulses. The number of pulses for layer B is 400 pulses, and the energy density is 0.25 J / cm². The number of pulses for layer A' is 6000 pulses.

[0104] In this embodiment, the number of components n within the multilayer A gradually increases from 5 to 6 to 8, resulting in a progressively stronger high-entropy effect. A component number gradient is formed between the top layer A (n=8) and the A2 layer (n=5). Layer B uses a simple oxide of two rare earth elements, Sm and Gd, further enriching the chemical environment of the heterogeneous interface. The anisotropic magnetoresistance performance of the composite thin film prepared in this embodiment is shown in the figure below. Figure 6 As shown.

[0105] Example 8: In this example, a multi-layer A / single-layer B / multi-layer A' structure is deposited on a Si substrate, with A and the internal composition gradient of A being symmetrically designed.

[0106] This embodiment describes a method for preparing a magnetoresistive high-entropy manganese oxide polycrystalline composite thin film with a heterostructure, comprising the following steps: Step 1: Substrate pretreatment. A p-type Si(111) substrate with a thickness of 300 μm and a surface area of ​​1 cm² was selected. The pretreatment procedure was the same as in Example 3.

[0107] Step 2: Target preparation.

[0108] A multilayer membrane consists of 3 sublayers: A-1 (bottom layer): (La) 0.30 Pr 0.25 Nd 0.25 Sm 0.20 ) 0.75 Ca 0.25 MnO3, n=5 A-2 (Middle Layer): (La) 0.25 Pr 0.25 Nd 0.25 Sm0.25 ) 0.75 Ca 0.2 5MnO3, n=5 A-3 (Top Floor): (La) 0.20 Pr 0.25 Nd 0.25 Sm 0.30 ) 0.75 Ca 0.25 MnO3, n=5 The multilayer A' consists of 3 sublayers (symmetrically designed with respect to A1): A'-1 (bottom layer): (La) 0.20 Pr 0.25 Nd 0.25 Sm 0.30 ) 0.75 Ca 0.25 MnO3, n=5 A'-2 (Middle Layer): (La) 0.25 Pr 0.25 Nd 0.25 Sm 0.25 ) 0.75 Ca 0.25 MnO3, n=5 A'-3 (Top Layer): (La) 0.30 Pr 0.25 Nd 0.25 Sm 0.20 ) 0.75 Ca 0.25 MnO3, n=5 The simple oxide target material is La2O3 (m=1).

[0109] The target preparation process is the same as in Example 1.

[0110] Steps 3 to 5: The deposition of the multi-layer film is the same as in Example 3, except that the deposition temperature is 620 ℃, the oxygen pressure is 18 Pa, the energy density is 1.70 J / cm², and the number of pulses for each sub-layer is 2500 pulses. The number of pulses for layer B is 150 pulses, and the energy density is 0.18 J / cm².

[0111] In this embodiment, the molar fraction of La in layer A decreases from 0.30 to 0.25 to 0.20, while the molar fraction of Sm increases from 0.20 to 0.25 to 0.30; in layer A', the molar fraction of La increases from 0.20 to 0.25 to 0.30, while the molar fraction of Sm decreases from 0.30 to 0.25 to 0.20, forming a symmetrical compositional gradient structure centered on layer B. This symmetrical gradient design is beneficial for balancing the internal stress distribution of the thin film and improving the uniformity of large-size thin films. The anisotropic magnetoresistance performance of the composite thin film prepared in this embodiment is shown in the figure below. Figure 7 As shown.

[0112] Comparative example: Using the same substrate pretreatment and target preparation process as in Example 1, only a single-layer A thin film ((La) was deposited. 0.25 Pr 0.25 Nd 0.25 Sm 0.25 ) 0.7 Ca 0.3 MnO3), without B and A' layers, and the deposition parameters are the same as those for layer A in Example 1. The magnetoresistance of the comparative film at room temperature and a magnetic field of 0.5T is only about 33% of that of Example 1, and the metal-insulator phase transition temperature deviates from room temperature by about 45K compared with Example 1.

[0113] The above embodiments demonstrate that by constructing a dispersed anisotropic heterostructure with a compositional gradient, the present invention significantly improves the room temperature magnetoresistance performance, anisotropic magnetoresistance effect, and temperature adaptability of high-entropy manganese oxide polycrystalline composite thin films, effectively solving the problem of insufficient performance of single-structure thin films in the prior art.

[0114] The technical solutions of this invention are not limited to the specific embodiments described above. Any technical modifications, alterations, substitutions, and variations made to the technical solutions of this invention without departing from the spirit and scope of the claims are within the protection scope of this invention.

Claims

1. A magnetoresistive high-entropy manganese oxide polycrystalline composite thin film with a heterostructure, characterized in that, Including those formed sequentially on the substrate: First high-entropy manganese oxide polycrystalline thin film layer (A layer); Simple oxide dispersed composite particle layer (B layer); Second high-entropy manganese oxide polycrystalline thin film layer (A' layer); The general chemical formulas of layer A and layer A' are respectively (H... x1 H x2 ...H xn MnO3 and (H') x1 H' x2 ...H' xn’ MnO3, wherein H and H' are each independently selected from the group containing La, Pr, Nd, Sm, Eu, Gd, Ca, and Sr, and H x1 ~H xn and H' x1 ~H' xn’ All elements are distinct, 5 ≤ n ≤ 8, 5 ≤ n' ≤ 8, and the mole fraction x of each element is given. i and x' i Each satisfies =1 and =1; The general chemical formula of the B layer is (S y1 S y2 ...S ym ) a O b , of which S y1 ~S ym For each element to be distinct, S is selected from the group containing La, Pr, Nd, Sm, Eu, Gd, Ca, and Sr, where 1 ≤ m ≤ 3, and the mole fraction y of each element is... i satisfy =1; A composition gradient exists between layers A and A', which is achieved by the following: the quantities of n and n' are different, and / or, for the same element, its mole fraction x i With x' i They are not the same.

2. The magnetoresistive high-entropy manganese oxide polycrystalline composite thin film with a heterogeneous structure according to claim 1, characterized in that, The A layer and / or A' layer are multi-film layer structures composed of multiple sub-film layers stacked together. A compositional gradient exists within the multi-film layer structure, achieved through the following means: the number of high-entropy components n in adjacent sub-film layers are different, and / or, for the same element, its mole fraction x... i They are not the same.

3. The magnetoresistive high-entropy manganese oxide polycrystalline composite thin film with a heterogeneous structure according to claim 1, characterized in that, When layer A or layer A' is a multi-film layer structure A' composed of multiple sub-film layers, a compositional gradient exists between the multi-film layer structure A' and the single film layer A. This is achieved by the following: the number of high-entropy components n of the sub-film layer closest to layer B in the multi-film layer structure A' is different from that of the adjacent single film layer A, and / or the mole fraction x of the same elements is different. i They are not the same.

4. The magnetoresistance high-entropy manganese oxide polycrystalline composite thin film with a heterogeneous structure according to claim 1, characterized in that, When both layers A and A' are multi-film layer structures composed of multiple sub-film layers, a compositional gradient exists between the two multi-film layer structures. This is achieved by the following: the number of high-entropy components n in the sub-film layers closest to layer B in the two multi-film layer structures are different, and / or the mole fraction x of the same elements are different. i They are not the same.

5. The magnetoresistive high-entropy manganese oxide polycrystalline composite thin film with a heterogeneous structure according to claim 1, characterized in that, The composition of layer B can be any one or a combination of the following: ① Simple oxides composed of a single element, i.e., m=1; ② Simple oxides composed of multiple elements, i.e., m=2 or 3; The combination specifically refers to: a simple oxide composed of multiple single elements, a simple oxide composed of multiple elements, or a combination of a single element and a simple oxide composed of multiple elements.

6. A method for preparing a magnetoresistive high-entropy manganese oxide polycrystalline composite thin film with a heterostructure as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Substrate pretreatment; Step 2, target preparation: high-entropy manganese oxide target and simple oxide target are prepared respectively; Step 3: The first high-entropy manganese oxide polycrystalline thin film layer (A layer) is deposited on the substrate using physical sputtering. Step four: Using physical sputtering, a composite particle layer (layer B) of simple oxide dispersed and anisotropically arranged is deposited on layer A. Step 5: Using physical sputtering, a second high-entropy manganese oxide polycrystalline thin film layer (A' layer) is deposited on the B layer.

7. The preparation method according to claim 6, characterized in that, In steps three and five, the process conditions for depositing layer A or layer A' are as follows: First, the high-entropy manganese oxide target material undergoes surface pre-deposition treatment, during which oxygen is introduced to maintain an oxygen pressure of 1.33 × 10⁻⁶. -5 Pa~1.33 Pa, pre-deposition pulse number 100 pulse~500 pulse, energy density 0.50 J / cm³ 2 ~1.00 J / cm 2 ; Then, formal deposition and growth took place, during which flowing oxygen was introduced to maintain an oxygen pressure of 1.33 Pa to 1.9 × 10⁻⁶ Pa. 4 Pa, deposition pulse number of 200 pulses to 30,000 pulses, energy density of 1.00 J / cm³ 2 ~2.00 J / cm 2 The substrate heating temperature is 200 ℃~800 ℃.

8. The preparation method according to claim 6, characterized in that, In step four, the process conditions for depositing the B layer are as follows: First, a surface pre-deposition treatment was performed on the simple oxide target material, during which oxygen was introduced to maintain an oxygen pressure of 1.33 × 10⁻⁶. -5 Pa~1.33 Pa, pre-deposition pulse number 100 pulse~500 pulse, energy density 0.50 J / cm³ 2 ~1.00 J / cm 2 ; Then, formal deposition and growth took place, during which flowing oxygen was introduced to maintain an oxygen pressure of 1.33 Pa to 1.9 × 10⁻⁶ Pa. 4 Pa, deposition pulse number from 1 to 1000 pulses, energy density of 0.05 J / cm³ 2 ~1.00 J / cm 2 The substrate heating temperature is 200 ℃~800 ℃.

9. The preparation method according to claim 7 or 8, characterized in that, The physical sputtering method is pulsed laser deposition or magnetron sputtering.

10. The preparation method according to claim 6, characterized in that, The substrate in step one is selected from SiN. δ One of Si or mica; the SiN δ The substrate thickness is 40 μm to 10000 μm, and δ = 1.00 to 1.33; the Si substrate thickness is 20 μm to 10000 μm, and the crystal plane index is [missing value]. <100> , <111> or <110> The type is P-type or N-type; the mica substrate is natural muscovite or fluorinated mica, with a thickness of 100μm~10000 μm and a surface roughness of ≤0.5 nm.

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