Bi-YIG thick film / permanent magnet nanowire array composite material

Abstract

The invention discloses a Bi-YIG thick film / permanent magnet nanowire array composite material, and belongs to the technical field of magnetic materials and microwave devices. A Bi-YIG thick film with the thickness of 20-50 microns grows on the surface of a substrate in a tape casting mode through a tape casting method, meanwhile, a permanent magnet nanowire array with the thickness of 20-100 microns grows on the surface of the Bi-YIG thick film through an electrochemical technology by means of an anodic aluminum oxide template, and magnetization of the Bi-YIG thick film is achieved by means of the high magnetic flux density characteristic of the permanent magnet nanowire array. And a similar composite material with a self-biasing function is formed. The composite material can solve the problem that a traditional circulator needs to be bonded with a permanent magnet, and a new thought is provided for preparing a self-biased circulator.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic materials and microwave devices, and particularly relates to a Bi-YIG thick film / permanent magnetic nanowire array composite material. Background Art

[0002] Microwave circulators are multi-port passive devices that, due to their forward transmission and reverse isolation characteristics, can function as switches for multi-channel electromagnetic signals. Circulators, designed based on the gyromagnetic properties of magnetic materials, are widely used in civilian devices such as 5G mobile communications, autonomous driving, drones, and robots. They also play an important role in the military, particularly in phased array radars. Consequently, they have attracted widespread attention and research from scholars both domestically and internationally in recent years.

[0003] The further development of active phased array radars has placed higher demands on microwave circulators. Circulators need to achieve self-biasing capabilities, effectively reducing their size and matching similar RF devices. They must also be integrated with monolithic microwave integrated circuit (MMIC) active chips. Currently, the United States has made the most rapid progress in self-biased circulator research. In 2019, the C-band self-biased circulator developed by Qorvo and Argonne National Laboratory had an insertion loss of 2.7dB, an isolation of 14dB, and dimensions of 10mm×6mm×0.1mm, making it 300 times smaller than traditional circulators in the same frequency band. In 2020, Qorvo and Metamagnetics collaborated to develop a Ka-band MMIC chip with a SiC substrate that integrates a self-biased circulator and a GaN HEMT power amplifier, achieving the integration of the circulator and active devices. In recent years, relevant domestic units have also carried out research on self-biased circulators. In 2021, the Ninth Institute of China Electronics Technology Group Corporation used hexagonal ferrite to make a self-biased circulator chip. Its performance reached the domestic advanced level, but it has not yet been integrated with active devices.

[0004] However, self-biased circulators developed by both domestic and international research institutions suffer from significant insertion loss. Furthermore, current hexagonal ferrite self-biased circulators are primarily bonded to semiconductor substrates, which can easily cause the device to fall off under extreme conditions, leading to device failure. Summary of the Invention

[0005] To address these issues, the present invention provides a Bi-YIG thick film / permanent magnetic nanowire array composite material. This composite material is a circulator with a quasi-self-biased structure. This quasi-self-biased structure reduces device losses and facilitates integration with active devices, broadening the application of self-biased circulators in active phased array radars.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention is to provide a Bi-YIG thick film / permanent magnetic nanowire array composite material, the structure of which includes: a substrate, a Bi-YIG thick film grown on the substrate, a metal electrode deposited on the surface of the Bi-YIG thick film, and a permanent magnetic nanowire array grown on the metal electrode; the thickness of the Bi-YIG thick film is 20 to 50 μm.

[0008] Preferably, the substrate is made of GaN, GaAs, SiC, Si, GGG or Al2O3.

[0009] Preferably, the ferromagnetic resonance linewidth of the Bi-YIG thick film is less than 150 Oe.

[0010] Preferably, the metal electrode is an Ag electrode.

[0011] More preferably, a Ni / Cr metal layer is further included between the Bi-YIG thick film and the Ag electrode.

[0012] The purpose of growing a Ni / Cr metal layer between the Bi-YIG thick film and the Ag electrode is to improve the bonding performance between the Bi-YIG thick film and the Ag electrode. The magnetron sputtered Cr reacts chemically with the Bi-YIG thick film, forming a chemical bond with good adhesion. The Cr layer and the Ni layer have similar physical properties and high bonding strength, and the Ni layer and the Ag layer are tightly bonded.

[0013] Preferably, the material of the permanent magnetic nanowire array is FePt, CoFe, FeNi, CuFe or ZnFe, and the structural dimensions are 20-100 μm in height, 20-500 nm in wire diameter, and 50-500 nm in wire spacing.

[0014] The second technical solution of the present invention is to provide a method for preparing the above-mentioned Bi-YIG thick film / permanent magnetic nanowire array composite material, comprising the following steps:

[0015] A Bi-YIG thick film is grown on one side of a substrate material, and then a metal electrode is grown on the surface of the Bi-YIG thick film. An AAO template with arrayed through holes is transferred onto the metal electrode, and a permanent magnetic material is deposited in the through holes of the AAO template. The AAO template is removed to obtain the Bi-YIG thick film / permanent magnetic nanowire array composite material.

[0016] Preferably, the method for growing the Bi-YIG thick film on one side of the substrate material is a tape casting method, wherein the crystallization of the Bi-YIG thick film is completed at a temperature of 850-950°C.

[0017] Specifically, the casting method includes the following steps:

[0018] (1) Preparation of Bi-YIG nanopowder by solid phase ball milling:

[0019] (2) mixing Bi-YIG powder and an organic carrier and ball milling to obtain a uniformly mixed slurry;

[0020] (3) applying the slurry to the substrate by tape casting to form a thick film;

[0021] (4) placing the thick film and substrate in a hot pressing furnace for heating and debinding;

[0022] (5) Sintering the thick film after debinding and cooling it to obtain a substrate with a Bi-YIG thick film grown on one side.

[0023] Further preferably, the molar purity of the components contained in the powder preparation raw material is 99.9%, the ball milling speed is 225-250 rpm, the ball milling time is preferably 12-24 hours, and the pre-calcination treatment is specifically: heating to 850°C at a heating rate of 2-3°C / min and keeping warm for 6 hours.

[0024] Further preferably, the components of the organic vehicle comprise, by mass percentage, 40-48% of terpineol, 40-48% of diethylene glycol butyl ether, 1-4% of triolein, 1-5% of butyl benzyl phthalate and 2-5% of ethyl cellulose.

[0025] The organic carrier is a powder and a solvent used for bonding and other solid powders mixed and dispersed into a paste slurry so that it can be printed on the target substrate using a tape casting method. The organic carrier is composed of an organic solvent, a dispersant, a plasticizer, a binder, etc., wherein the organic solvent determines the rheological properties and volatility of the organic carrier. The organic solvent used in the present invention is composed of terpineol and diethylene glycol butyl ether. In addition, the present invention adds a dispersant triolein so that the powder is more evenly distributed in the organic solvent. Ethyl cellulose can be coordinated with terpineol to regulate the viscosity of the slurry so that the slurry can be better tape cast on the substrate. Butyl benzyl phthalate enables the tape casting to obtain a thick film that can maintain a good morphology during heating and better adhere to the substrate.

[0026] More preferably, the Bi-YIG powder accounts for 50%-70% of the total mass.

[0027] The specific operation of the casting is: placing the substrate into a casting machine and casting the slurry from the template onto the substrate by a scraper to form a thick film.

[0028] More preferably, a hot pressing furnace is used to perform hot pressing and debinding operation on the thick film, with a heating temperature of 300-350° C., a holding time of 60-120 min, and an applied pressure of 5-10 MPa.

[0029] Further preferably, the specific operation of sintering is: placing a load on the thick film and then placing it in an air atmosphere, heating it to the sintering temperature, and sintering it for 6-10 hours; the heating rate is 2-3°C / min, and the sintering temperature is 850-950°C.

[0030] Further preferably, the substrate is an Al2O3 ceramic plate.

[0031] Preferably, the method of growing the metal electrode on the surface of the Bi-YIG thick film is magnetron sputtering.

[0032] The third technical solution of the present invention: provides an application of the above-mentioned Bi-YIG thick film / permanent magnetic nanowire array composite material in the preparation of a self-biased circulator.

[0033] The beneficial technical effects of the present invention are as follows:

[0034] The present invention induces the growth of a 20-50 μm Bi-YIG thick film on the surface of a substrate by a tape casting method (YIG ferrite replaces hexagonal ferrite, which has certain advantages in reducing device losses). The YIG thick film is selected to replace the block material of the traditional self-biased circulator, which is easier to integrate with the substrate. In addition, the YIG gyromagnetic effect is good, the resonance linewidth is small, and the microwave electromagnetic loss is low, which is more conducive to improving device performance. At the same time, a permanent magnetic nanowire array is grown on the surface of the Bi-YIG thick film through electrochemical technology and with the help of an anodic aluminum oxide template. The high magnetic flux density characteristics of the permanent magnetic nanowire array are used to achieve magnetization of the Bi-YIG thick film, forming a composite material similar to that with self-biasing function. This composite material can solve the problem that traditional circulators need to be bonded with permanent magnets, and avoids the high loss characteristics of self-biased hexagonal ferrite materials, providing a new idea for the preparation of self-biased circulators. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic structural diagram of the Al2O3 substrate / Bi-YIG thick film / permanent magnetic nanowire array composite material prepared in Example 1 of the present invention.

[0036] Figure 2 This is a preparation flow chart of Example 1 of the present invention.

[0037] Figure 3 This is the XRD pattern of the Bi-YIG thick film in the composite material obtained in Example 1 of the present invention.

[0038] Figure 4 This is the XRD pattern of CoFe magnetic nanowires in the composite material obtained in Example 1 of the present invention.

[0039] Figure 5 This is a SEM image of the Bi-YIG thick film in the composite material obtained in Example 1 of the present invention.

[0040] Figure 6 This is an SEM image of CoFe magnetic nanowires in the composite material obtained in Example 1 of the present invention.

[0041] Figure 7 This is the magnetization curve of the Bi-YIG thick film in the composite material obtained in Example 1 of the present invention.

[0042] Figure 8 This is the hysteresis loop of the CoFe magnetic nanowires in the composite material obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0043] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0044] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention.

[0046] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0047] Example 1

[0048] Preparation of Al2O3 substrate / Bi-YIG thick film / permanent magnetic nanowire array composite material:

[0049] (1) Growth of Bi-YIG thick film on Al2O3 substrate

[0050] Bi-YIG nanopowders were prepared by solid phase ball milling. Y2O3, Fe2O3, CuO, SnO2, and Bi2O3 powders with a purity of 99.9% were mixed in a certain molar ratio to prepare Y 2.2 Bi 0.8 Fe 4.8 Cu 0.1 Sn0.1 O 12 Powder; Place the mixed powder in a ball mill jar with ball milling beads. Add 1.2 times the mass of anhydrous ethanol to the jar. Place the jar in a ball mill and mill at 250 rpm for 12 hours. Remove the milled powder and dry it in a 60°C oven. Grind the dried product into powder and place it in a crucible. Pre-calculate in a muffle furnace. Ramp up at a rate of 2°C / min; pre-calculate to 850°C for 6 hours. Cool down at a rate of 2°C / min.

[0051] The intermediate layer powder was sieved through 80 and 120 mesh sieves, and mixed with an organic vehicle mass: Bi-YIG powder mass ratio of 4:6. The organic vehicle consisted of the following components in mass percentage: 45% terpineol, 45% diethylene glycol butyl ether, 3% triolein, 3% butyl benzyl phthalate, and 4% ethyl cellulose. First, the powder, terpineol, diethylene glycol butyl ether, and triolein were placed in a ball mill and milled for 12 hours. Subsequently, ethyl cellulose and butyl benzyl phthalate were added and ball milled again for 12 hours. Then, the tape casting process was carried out. The distance between the blade and the substrate was 100 μm, the casting speed was 300 mm / min, and the tape was dried at 60°C after the casting process.

[0052] The dried thick film was placed at 300°C and 10 MPa for 120 minutes for debinding. The thick film was then placed in a muffle furnace and kept at 900°C for 6 hours to obtain a Bi-YIG thick film.

[0053] (2) Magnetron sputtering of Cr, Ni, and Ag on the surface of Bi-YIG thick film

[0054] Cr, Ni, and Ag metals were sequentially magnetron sputtered on the surface of the Bi-YIG thick film of the Al2O3 substrate / Bi-YIG thick film obtained in step (1), and the background vacuum of the coating chamber was evacuated to 1×10 -2 Pa, introduce Ar gas at a flow rate of 100 mL / min, the furnace pressure is 0.5 Pa, turn on the palladium power supply to plate Cr, Ni, and Ag respectively, and obtain Ag / Ni / Cr / Bi-YIG / substrate;

[0055] (3) Growth of permanent magnetic nanowire arrays on the Ag surface

[0056] An AAO template with through-holes (hole diameter of 20 nm, pore spacing of 65 nm, and pore depth of 25 μm) was prepared by an electrochemical method and then transferred to the metal layer of the Ag / Ni / Cr / Bi-YIG / substrate in step (2). CoFe was then deposited in the through-holes by an electrochemical deposition process.

[0057] A 1μmAg electrode was plated on one side of the prepared double-pass AAO template. A mixed solution containing 0.03 mol / L cobalt sulfate heptahydrate, 0.4 mol / L boric acid, 0.1 g ascorbic acid, and 0.06 mol / L ferrous sulfate heptahydrate was then prepared with 100 mL of deionized water. The solution was thoroughly dissolved using an ultrasonic cleaner and the pH was adjusted to 3 with 1 M dilute sulfuric acid. The electrode-coated AAO template was placed in a template holder as the working electrode, and potentiostatic electrodeposition was performed using an electrochemical workstation. After electroplating, a 5 mol / L NaOH solution was prepared and heated to 60°C to dissolve the AAO template. Finally, the template was rinsed with anhydrous ethanol to produce CoFe magnetic nanowires.

[0058] After removing the AAO template, an Al2O3 substrate / Bi-YIG thick film / permanent magnetic nanowire array composite material was obtained.

[0059] Figure 1 This is a schematic structural diagram of the Al2O3 substrate / Bi-YIG thick film / permanent magnetic nanowire array composite material prepared in Example 1 of the present invention.

[0060] Figure 2 This is a flow chart of the preparation of Example 1 of the present invention.

[0061] Performance Testing

[0062] The Bi-YIG thick film and CoFe magnetic nanowires were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM) and vibrating magnetometer (VSM), respectively.

[0063] XRD test results: Figure 3 The test results of Bi-YIG thick film are shown in Figure 2. Figure 4 The test results of CoFe magnetic nanowires are shown in Figure 4. By comparing all the peak positions of the thick film sample with the standard peak positions from PDF 43-0507, it is obvious that the diffraction peaks of the doped sample coincide with the peak positions of YIG, which proves that Bi 3+ The ions are almost completely integrated into the YIG lattice. Figure 4 The peaks of CoFe magnetic nanowires are relatively weak, and the main characteristic peaks are (440)(311)(511), which is related to the relatively strong peaks of silicon substrate.

[0064] SEM test results: Figure 5 The test results of Bi-YIG thick film are shown in Figure 2. Figure 6 The test results of CoFe magnetic nanowires. Figure 5 It can be seen that the Bi-YIG thick film grown on Al2O3 is relatively dense, with only a small amount of pores, uniform grain distribution, and a thickness of about 25μm. Figure 6It shows that the spacing between CoFe magnetic nanowires is 65nm, the diameter is about 20nm, and the distribution is relatively uniform.

[0065] VSM test results: Figure 7 is the magnetization curve of Bi-YIG thick film, Figure 8 is the hysteresis loop of CoFe magnetic nanowire. Figure 7 Very obvious soft magnetic characteristics can be observed in the Bi-YIG thick film. The saturation magnetization of the Bi-YIG thick film is 23.9emu / g. The high saturation magnetization of the Bi-YIG thick film requires a uniform and dense microstructure. The magnetic properties of the Bi-YIG thick film are lower than the theoretical value of 26.8emu / g due to the large amount of Bi 3+ Elements. From Figure 8 It can be seen that the CoFe magnetic nanowires have strong anisotropy and a remanence ratio of 0.74; they can provide a good magnetization function for thick films.

[0066] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A Bi-YIG thick film / permanent magnetic nanowire array composite material, characterized in that: The structure includes: A substrate, a Bi-YIG thick film grown on the substrate, a metal electrode deposited on the surface of the Bi-YIG thick film, and a permanent magnetic nanowire array grown on the metal electrode; the thickness of the Bi-YIG thick film is 20 to 50 μm.

2. The Bi-YIG thick film / permanent magnetic nanowire array composite material according to claim 1, characterized in that: The substrate is made of GaN, GaAs, SiC, Si, GGG or Al2O3.

3. The Bi-YIG thick film / permanent magnetic nanowire array composite material according to claim 1, characterized in that: The ferromagnetic resonance line width of the Bi-YIG thick film is less than 150 Oe.

4. The Bi-YIG thick film / permanent magnetic nanowire array composite material according to claim 1, characterized in that: The metal electrode is an Ag electrode.

5. The Bi-YIG thick film / permanent magnetic nanowire array composite material according to claim 4, characterized in that: A Ni / Cr metal layer is further included between the Bi-YIG thick film and the Ag electrode.

6. The Bi-YIG thick film / permanent magnetic nanowire array composite material according to claim 1, characterized in that: The material of the permanent magnetic nanowire array is FePt, CoFe, FeNi, CuFe or ZnFe, and the structural dimensions are 20-100 μm in height, 100-500 nm in wire diameter, and 100-500 nm in wire spacing.

7. A method for preparing the Bi-YIG thick film / permanent magnetic nanowire array composite material according to any one of claims 1 to 6, characterized in that: The following steps are involved: A Bi-YIG thick film is grown on one side of a substrate material, and then a metal electrode is grown on the surface of the Bi-YIG thick film. An AAO template with arrayed through holes is transferred onto the metal electrode, and a permanent magnetic material is deposited in the through holes of the AAO template. The AAO template is removed to obtain the Bi-YIG thick film / permanent magnetic nanowire array composite material.

8. The preparation method according to claim 7, characterized in that The method for growing the Bi-YIG thick film on one side of the substrate material is a tape casting method, wherein the crystallization of the Bi-YIG thick film is completed at a temperature of 850-950°C.

9. The preparation method according to claim 7, characterized in that The method for growing the metal electrode on the surface of the Bi-YIG thick film is magnetron sputtering.

10. Use of the Bi-YIG thick film / permanent magnetic nanowire array composite material according to any one of claims 1 to 6 in preparing a self-biased circulator.

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