A spin terahertz emission device and a preparation method and application thereof

Abstract

The application provides a spin terahertz emission device and a preparation method and application thereof, and relates to the technical field of terahertz emission. The spin terahertz emission device provided by the application comprises a ferromagnetic material layer, an antiferromagnetic layer and a non-ferromagnetic layer which are sequentially arranged in layers. In the application, the ferromagnetic material layer is adjacent to the antiferromagnetic layer, the antiferromagnetic layer is used to fix the magnetization direction of the lower ferromagnetic layer, so that spin terahertz emission can be realized under the condition that the external magnetic field is removed. The application can realize efficient spin terahertz radiation by using the antiferromagnetic layer / non-ferromagnetic layer heterojunction. In the application, the antiferromagnetic layer generates spin current under laser irradiation and has a 'transmission effect' on the spin current. In the structure of the application, the spin current is derived from the ferromagnetic layer and the antiferromagnetic layer, so that the generation efficiency of the spin polarized current can be greatly improved, and the terahertz radiation efficiency can be greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of terahertz emission, in particular to a spin terahertz emission device and a preparation method and application thereof. BACKGROUND

[0002] For terahertz emission, the commonly used terahertz (THz) sources at present include photoconductive antenna terahertz source and spin terahertz source. The photoconductive antenna terahertz source is composed of a semiconductor substrate and an electrode, and its working principle is that a beam of ultra-short pulse laser is focused on the semiconductor material between the electrodes. If the laser photon energy is greater than the energy gap width of the semiconductor substrate material, the electrons can be excited to the conduction band to form photo-generated carriers. These photo-generated carriers move under the action of the bias electric field to form a transient changing current in the laser penetration depth range, and then radiate terahertz waves. The photoconductive antenna terahertz source has the defects of high price and poor preservation.

[0003] For the spin terahertz source, it is generally composed of a ferromagnetic material / non-ferromagnetic material heterojunction, and its working principle is that when a femtosecond laser pulse irradiates the ferromagnetic material / non-ferromagnetic material hetero-bilayer film, an ultrafast spin current is excited in the ferromagnetic layer. When the spin current enters the non-ferromagnetic layer, the inverse spin Hall effect causes it to change into a transient charge current, thereby radiating terahertz.

[0004] Chinese patent CN109300922A discloses a high-efficiency terahertz emission chip based on electron spin, which takes a ferromagnetic layer / metal layer / oxide barrier layer / pinning layer / anti-ferromagnetic pinning layer as a basic emission structure. Without applying an external magnetic field, the terahertz radiation efficiency, bandwidth and polarization state are controlled by controlling the different materials and film thicknesses in the composite film structure. However, the emission device provided by this scheme has film layers (anti-ferromagnetic pinning layer and barrier layer) that are not used for emission, which can absorb laser or terahertz, thereby reducing the emission efficiency.

[0005] In 2020, the Institute of Physics of the University of Augsburg in Germany realized the modulation of terahertz amplitude by changing the direction of the external magnetic field in the structure of ferromagnetic layer / non-ferromagnetic layer / ferromagnetic layer / anti-ferromagnetic pinning layer, and utilized the tunneling magnetoresistance effect (DOI: 10.1109 / IRMMW-THz50926.2021.9567227). This scheme needs an external magnetic field, and also has the defect of low emission efficiency. SUMMARY

[0006] The present application aims to provide a spin terahertz emission device and a preparation method and application thereof. The spin terahertz emission device provided by the present application can realize field-free spin terahertz emission, and has high emission efficiency.

[0007] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0008] The application provides a spin terahertz emission device, comprising a ferromagnetic material layer, an antiferromagnetic layer and a non-ferromagnetic layer which are sequentially stacked.

[0009] Preferably, the thickness of the spin terahertz emission device is 25-130 nm.

[0010] Preferably, the thickness of the ferromagnetic material layer is 2-10 nm.

[0011] Preferably, the component of the ferromagnetic material layer is a two-dimensional ferromagnetic material or a ferromagnetic metal.

[0012] Preferably, the thickness of the antiferromagnetic layer is 10-100 nm.

[0013] Preferably, the component of the antiferromagnetic layer is a single-crystal antiferromagnetic material.

[0014] Preferably, the thickness of the non-ferromagnetic layer is 2-15 nm.

[0015] Preferably, the component of the non-ferromagnetic layer is a topological material.

[0016] The application provides a preparation method of the spin terahertz emission device.

[0017] The ferromagnetic material layer, the antiferromagnetic layer and the non-ferromagnetic layer are sequentially prepared on the surface of a substrate to obtain the spin terahertz emission device.

[0018] The application provides an application of the spin terahertz emission device in field-free spin terahertz emission.

[0019] The application provides a spin terahertz emission device, comprising a ferromagnetic material layer, an antiferromagnetic layer and a non-ferromagnetic layer which are sequentially stacked. In the application, the ferromagnetic material layer is adjacent to the antiferromagnetic layer, the magnetization direction of the lower ferromagnetic layer is fixed by the antiferromagnetic layer, and spin terahertz emission can be realized under the condition of removing an external magnetic field. The application can realize high-efficiency spin terahertz radiation by using an antiferromagnetic layer / non-ferromagnetic layer heterojunction. In the application, the antiferromagnetic layer generates a spin current under laser irradiation and has a “transmission effect” on the spin current. In the structure of the application, the spin current is derived from the ferromagnetic layer and the antiferromagnetic layer, and the generation efficiency of the spin-polarized current can be greatly improved. The application can greatly improve the terahertz radiation efficiency.

[0020] The spin terahertz emission device provided by the application has a wide temperature range and stable material properties in the temperature range of 0-300 K, and can guarantee the reliability of the device. The device can realize high-efficiency spin terahertz radiation in a wide band in the temperature range of 0-300 K.

[0021] Preferably, the spin terahertz emission device provided by the present invention has a small thickness, which is a significant step towards achieving high efficiency and miniaturization of spin terahertz sources. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the spin terahertz emission device provided by the present invention. Detailed Implementation

[0023] The present invention provides a spin terahertz emission device, comprising a ferromagnetic material layer, an antiferromagnetic layer and a nonferromagnetic layer stacked sequentially.

[0024] In this invention, the thickness of the spin terahertz emitting device is preferably 25–130 nm, more preferably 50–100 nm.

[0025] The spin terahertz emission device provided by this invention includes a ferromagnetic material layer. In this invention, the thickness of the ferromagnetic material layer is preferably 2–10 nm, more preferably 5–8 nm.

[0026] In this invention, the composition of the ferromagnetic material layer is preferably a two-dimensional ferromagnetic material or a ferromagnetic metal. In this invention, the two-dimensional ferromagnetic material preferably includes Fe. x GeTe2 or CrTe2; the Fe x The x in GeTe2 is preferably 3 to 5, more preferably 4; the composition of the ferromagnetic metal preferably includes one or more of Co, Fe and Ni, more preferably Co, Fe or Ni.

[0027] The spin terahertz emission device provided by this invention includes an antiferromagnetic layer disposed on the surface of the ferromagnetic material layer. In this invention, the thickness of the antiferromagnetic layer is preferably 10–100 nm, more preferably 15–80 nm. In this invention, the antiferromagnetic layer is adjacent to the ferromagnetic material layer. Due to the exchange bias characteristic of the antiferromagnetic layer itself, it can produce a pinning effect on the adjacent ferromagnetic material layer, that is, it can completely magnetize the internal magnetic moments of the ferromagnetic material layer without the need for an external magnetic field. Therefore, no additional magnetic field is required in terahertz emission.

[0028] In this invention, the composition of the antiferromagnetic layer is preferably a single-crystal antiferromagnetic material, more preferably NiO or CrSb. In this invention, the "transfer" effect of NiO on spin current can greatly improve the generation efficiency of spin-polarized current, and further improve the efficiency of terahertz radiation. Taking 111 phase NiO as an example, ... Figure 1 As shown, under femtosecond laser irradiation, the NiO thin film generates a net magnetic moment M through nonlinear optical effects, and the precession of M generates a spin polarization current J. s1 After a spin current is injected into an adjacent nonferromagnetic layer, a transient charge flow J is generated due to the inverse spin Hall effect. cThis leads to the emission of terahertz waves. When a laser irradiates a ferromagnetic material layer, due to the ultrafast demagnetization and superdiffusion processes, the ferromagnetic thin film will generate a spin-polarized current J. s2 When this spin-polarized current flows into an adjacent NiO thin film, it generates a magnon current J. M When the magnon current flows into the adjacent non-ferromagnetic layer, it also generates a transient current through the inverse spin Hall effect, thereby radiating terahertz waves. The above process shows that in the spin terahertz emitting device provided by this invention, the terahertz waves originate from two parts, and because J... s1 and J s2 Since they are in the same direction, the two terahertz waves are in phase, achieving the effect of amplitude superposition, which in turn significantly improves the emission efficiency of terahertz waves.

[0029] The spin terahertz emission device provided by the present invention includes a non-ferromagnetic layer disposed on the surface of the antiferromagnetic layer. In the present invention, the thickness of the non-ferromagnetic layer is preferably 2-15 nm, more preferably 3-10 nm.

[0030] In this invention, the composition of the non-ferromagnetic layer is preferably a topological material, more preferably a topological insulator, a topological half-metal, or a heavy metal. In this invention, the topological insulator preferably includes Bi₂Se₃, Bi₂Te₃, or Bi₂Se₃. x Sb 1-x Sb2Te3 or (Bi x Sb 1-x )2Te3; the Bi x Sb 1-x x is preferably 0 to 1; the (Bi) x Sb 1-x In 2Te3, x is preferably 0 to 1. In this invention, the topological half-metal preferably includes PtTe2 or WTe2. In this invention, the heavy metal preferably includes W, Ta, or Pt.

[0031] The spin terahertz emitting device provided by the present invention emits broadband terahertz waves in the range of 0 to 300K by irradiation with an 800nm ​​or 1560nm femtosecond laser without the aid of an external magnetic field; the bandwidth of the broadband terahertz waves is in the range of 0 to 30THz.

[0032] This invention provides a method for fabricating the spin terahertz emission device described above, comprising the following steps:

[0033] A spin terahertz emission device is obtained by sequentially fabricating a ferromagnetic material layer, an antiferromagnetic layer, and a nonferromagnetic layer on the substrate surface.

[0034] In this invention, the substrate is preferably made of alumina or magnesium oxide. Specifically, the alumina is preferably double-polished alumina, and the magnesium oxide is preferably double-polished magnesium oxide. Before preparing the ferromagnetic material layer, the substrate is preferably cleaned. The cleaning preferably includes sequential acetone washing, isopropanol washing, and water washing. The cleaning is preferably performed under ultrasonic conditions. This invention removes organic matter from the substrate surface through cleaning.

[0035] In this invention, the ferromagnetic material layer is preferably prepared by molecular beam epitaxy, magnetron sputtering or pulsed laser deposition.

[0036] In this invention, the antiferromagnetic layer is preferably prepared by molecular beam epitaxy, magnetron sputtering or pulsed laser deposition.

[0037] In this invention, the non-ferromagnetic layer is preferably prepared by molecular beam epitaxy, magnetron sputtering or pulsed laser deposition.

[0038] This invention provides the application of the spin terahertz emitting device described above in field-free spin terahertz emission. In a specific application example of this invention, the spin terahertz emitting device is placed in a variable-temperature terahertz time-domain spectroscopy system to radiate terahertz waves. In this invention, the temperature range of the variable-temperature terahertz time-domain spectroscopy system is 0–300 K.

[0039] Traditional spin terahertz radiation sources include ferromagnetic / nonferromagnetic heterojunctions, ferromagnetic / nonferromagnetic / ferromagnetic heterojunctions, and antiferromagnetic (single crystal) / nonferromagnetic heterojunctions. Their spin current originates only from either the ferromagnetic or antiferromagnetic layer, meaning they have only one source, limiting terahertz emission efficiency. Furthermore, most require an external magnetic field, restricting the simplification of spin terahertz emission. Moreover, most spin terahertz experiments are conducted only at room temperature, with very little research at low temperatures. The spin terahertz emission device provided by this invention has a ferromagnetic / antiferromagnetic / nonferromagnetic heterojunction, with its spin current originating from both the ferromagnetic and antiferromagnetic layers. Compared to current spin terahertz sources, the spin current generation efficiency is greatly improved, thus enhancing spin terahertz emission efficiency. Moreover, the characteristics of antiferromagnetic exchange bias and coercive field are more pronounced at low temperatures (0–300 K). That is, at low temperatures, antiferromagnets are more likely to "pin" the magnetic moment of the ferromagnetic layer. Therefore, the present invention provides a spin terahertz emission device that can still be used at low temperatures and can achieve terahertz emission without field strength.

[0040] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0041] Example 1

[0042] (1) Cleaning the substrate: Place the double-polished alumina substrate in acetone and isopropanol for 5-6 minutes each, then in deionized water for 5-6 minutes, and dry it with nitrogen before placing it in the growth chamber.

[0043] (2) Preparation of ferromagnetic material layers using molecular beam epitaxy: The vacuum level of the molecular beam epitaxy growth cavity is maintained at 10. -10 In the Torr ultra-high vacuum chamber, evaporation sources Fe, Ge, and Te are installed. The evaporation rate is determined by a film thickness monitoring instrument (FDC) to control the flux ratio during the growth process. After the substrate temperature reaches 600°C, annealing is performed for 60 min, and then the substrate temperature is reduced to 280°C for growth. The evaporation rate of the Fe evaporation source is 0.5 nm / min, the evaporation rate of the Ge evaporation source is 0.1 nm / min, and the evaporation rate of the Te evaporation source is 0.5 nm / min. The thickness of the resulting ferromagnetic material layer Fe4GeTe2 is 4 nm.

[0044] (3) An antiferromagnetic layer was prepared using pulsed laser deposition: the target material was Ni, the distance between the substrate and the target was set to 6 cm, the laser wavelength was 355 nm, the repetition frequency was 10 Hz, and the energy was 35 mJ / pulse; after the substrate was heated to 600 °C, the antiferromagnetic layer was deposited under an oxygen pressure of 3 × 10⁻⁶ mJ / pulse. -2 Thin film deposition was performed at Pa to obtain an antiferromagnetic NiO layer with a thickness of 40 nm.

[0045] (4) Fabrication of nonferromagnetic layers using molecular beam epitaxy: The vacuum level of the molecular beam epitaxy growth cavity is maintained at 10. - 10 In the Torr ultra-high vacuum chamber, evaporation sources Bi and Te are installed. The evaporation rate is determined by a film thickness monitoring instrument (FDC) to control the flux ratio during the growth process. After the substrate temperature reaches 600°C, annealing is performed for 60 min, and then the substrate temperature is reduced to 235°C for growth. The evaporation rate of the Bi evaporation source is 0.15 nm / min, and the evaporation rate of the Te evaporation source is 1.5 nm / min. The thickness of the resulting non-ferromagnetic layer Bi2Te3 is 8 nm.

[0046] A schematic diagram of the spin terahertz emission device prepared in this embodiment is shown below. Figure 1As shown. When the spin terahertz emitting device prepared in this embodiment is placed in a variable-temperature (0-300K) terahertz time-domain spectroscopy system, it can emit terahertz waves under conditions without an external magnetic field, and the emission efficiency is high.

[0047] Example 2

[0048] (1) Cleaning the substrate: Place the double-polished alumina substrate in acetone and isopropanol for 5-6 minutes each, then in deionized water for 5-6 minutes, and dry it with nitrogen before placing it in the growth chamber.

[0049] (2) Preparation of ferromagnetic material layers using molecular beam epitaxy: The vacuum level of the molecular beam epitaxy growth cavity is maintained at 10. -10 Torr, an evaporation source Fe is installed in an ultra-high vacuum chamber, and the evaporation rate is determined by a film thickness monitoring instrument (FDC) to control the flux ratio during the growth process. After the substrate temperature reaches 600°C, it is annealed for 60 min, and then the substrate temperature is reduced to 1200°C for growth. The evaporation rate of the Fe evaporation source is 0.3 nm / min, and the thickness of the resulting ferromagnetic material layer is 3 nm.

[0050] (3) An antiferromagnetic layer was prepared using pulsed laser deposition: the target material was Ni, the distance between the substrate and the target was set to 6 cm, the laser wavelength was 355 nm, the repetition frequency was 10 Hz, and the energy was 35 mJ / pulse; after the substrate was heated to 600 °C, the antiferromagnetic layer was deposited under an oxygen pressure of 3 × 10⁻⁶ mJ / pulse. -2 Thin film deposition was performed at Pa to obtain an antiferromagnetic NiO layer with a thickness of 40 nm.

[0051] (4) Fabrication of nonferromagnetic layers using molecular beam epitaxy: The vacuum level of the molecular beam epitaxy growth cavity is maintained at 10. - 10 In the Torr ultra-high vacuum chamber, evaporation sources Bi and Te are installed. The evaporation rate is determined by a film thickness monitoring instrument (FDC) to control the flux ratio during the growth process. After the substrate temperature reaches 600°C, annealing is performed for 60 min, and then the substrate temperature is reduced to 235°C for growth. The evaporation rate of the Bi evaporation source is 0.15 nm / min, and the evaporation rate of the Te evaporation source is 1.5 nm / min. The thickness of the resulting non-ferromagnetic layer Bi2Te3 is 8 nm.

[0052] A schematic diagram of the spin terahertz emission device prepared in this embodiment is shown below. Figure 1 As shown. When the spin terahertz emitting device prepared in this embodiment is placed in a variable-temperature (0-300K) terahertz time-domain spectroscopy system, it can emit terahertz waves under conditions without an external magnetic field, and the emission efficiency is high.

[0053] Example 3

[0054] (1) Cleaning the substrate: Place the double-polished alumina substrate in acetone and isopropanol for 5-6 minutes each, then in deionized water for 5-6 minutes, and dry it with nitrogen before placing it in the growth chamber.

[0055] (2) Preparation of ferromagnetic material layers using molecular beam epitaxy: The vacuum level of the molecular beam epitaxy growth cavity is maintained at 10. -10 In the Torr ultra-high vacuum chamber, evaporation sources Fe, Ge, and Te are installed. The evaporation rate is determined by a film thickness monitoring instrument (FDC) to control the flux ratio during the growth process. After the substrate temperature reaches 600°C, annealing is performed for 60 min, and then the substrate temperature is reduced to 280°C for growth. The evaporation rate of the Fe evaporation source is 0.5 nm / min, the evaporation rate of the Ge evaporation source is 0.1 nm / min, and the evaporation rate of the Te evaporation source is 0.5 nm / min. The thickness of the resulting ferromagnetic material layer Fe4GeTe2 is 4 nm.

[0056] (3) An antiferromagnetic layer was prepared using pulsed laser deposition: the target material was Ni, the distance between the substrate and the target was set to 6 cm, the laser wavelength was 355 nm, the repetition frequency was 10 Hz, and the energy was 35 mJ / pulse; after the substrate was heated to 600 °C, the antiferromagnetic layer was deposited under an oxygen pressure of 3 × 10⁻⁶ mJ / pulse. -2 Thin film deposition was performed at Pa to obtain an antiferromagnetic NiO layer with a thickness of 40 nm.

[0057] (4) Fabrication of nonferromagnetic layers using molecular beam epitaxy: The vacuum level of the molecular beam epitaxy growth cavity is maintained at 10. - 10 In the Torr ultra-high vacuum chamber, evaporation sources Pt and Te are installed. The evaporation rate is determined by a film thickness monitoring instrument (FDC) to control the flux ratio during the growth process. After the substrate temperature reaches 600°C, annealing is performed for 60 min, and then the substrate temperature is reduced to 300°C for growth. The evaporation rate of the Pt evaporation source is 0.5 nm / min, and the evaporation rate of the Te evaporation source is 1.5 nm / min. The thickness of the resulting non-ferromagnetic layer PtTe2 is 15 nm.

[0058] A schematic diagram of the spin terahertz emission device prepared in this embodiment is shown below. Figure 1 As shown. When the spin terahertz emitting device prepared in this embodiment is placed in a variable-temperature (0-300K) terahertz time-domain spectroscopy system, it can emit terahertz waves under conditions without an external magnetic field, and the emission efficiency is high.

[0059] Example 4

[0060] (1) Cleaning the substrate: Place the double-polished alumina substrate in acetone and isopropanol for 5-6 minutes each, then in deionized water for 5-6 minutes, and dry it with nitrogen before placing it in the growth chamber.

[0061] (2) Preparation of ferromagnetic material layers using molecular beam epitaxy: The vacuum level of the molecular beam epitaxy growth cavity is maintained at 10. -10 In the Torr ultra-high vacuum chamber, evaporation sources Fe, Ge, and Te are installed. The evaporation rate is determined by a film thickness monitoring instrument (FDC) to control the flux ratio during the growth process. After the substrate temperature reaches 600°C, annealing is performed for 60 min, and then the substrate temperature is reduced to 280°C for growth. The evaporation rate of the Fe evaporation source is 0.5 nm / min, the evaporation rate of the Ge evaporation source is 0.1 nm / min, and the evaporation rate of the Te evaporation source is 0.5 nm / min. The thickness of the resulting ferromagnetic material layer Fe4GeTe2 is 4 nm.

[0062] (3) An antiferromagnetic layer was prepared using pulsed laser deposition: the target material was Ni, the distance between the substrate and the target was set to 6 cm, the laser wavelength was 355 nm, the repetition frequency was 10 Hz, and the energy was 35 mJ / pulse; after the substrate was heated to 600 °C, the antiferromagnetic layer was deposited under an oxygen pressure of 3 × 10⁻⁶ mJ / pulse. -2 Thin film deposition was performed at Pa to obtain an antiferromagnetic NiO layer with a thickness of 40 nm.

[0063] (4) Fabrication of nonferromagnetic layers using molecular beam epitaxy: The vacuum level of the molecular beam epitaxy growth cavity is maintained at 10. - 10 Torr uses an evaporation source of Pt installed in an ultra-high vacuum chamber. The evaporation rate is determined by a film thickness monitoring instrument (FDC) to control the flux ratio during the growth process. After the substrate temperature reaches 600°C, it is annealed for 60 minutes and then the substrate temperature is reduced to room temperature for growth. The evaporation rate of the Pt evaporation source is 0.5 nm / min, and the thickness of the resulting non-ferromagnetic layer is 3 nm.

[0064] A schematic diagram of the spin terahertz emission device prepared in this embodiment is shown below. Figure 1 As shown. When the spin terahertz emitting device prepared in this embodiment is placed in a variable-temperature (0-300K) terahertz time-domain spectroscopy system, it can emit terahertz waves under conditions without an external magnetic field, and the emission efficiency is high.

[0065] Example 5

[0066] (1) Cleaning the substrate: Place the double-polished alumina substrate in acetone and isopropanol for 5-6 minutes each, then in deionized water for 5-6 minutes, and dry it with nitrogen before placing it in the growth chamber.

[0067] (2) Preparation of ferromagnetic material layers using molecular beam epitaxy: The vacuum level of the molecular beam epitaxy growth cavity is maintained at 10. -10 Torr, an evaporation source Fe is installed in an ultra-high vacuum chamber, and the evaporation rate is determined by a film thickness monitor (FDC) to control the flux ratio during the growth process. After the substrate temperature reaches 600°C, it is annealed for 60 min, and then the substrate temperature is reduced to room temperature for growth. The evaporation rate of the Fe evaporation source is 0.5 nm / min, and the thickness of the resulting ferromagnetic material layer is 3 nm.

[0068] (3) An antiferromagnetic layer was prepared using pulsed laser deposition: the target material was Ni, the distance between the substrate and the target was set to 6 cm, the laser wavelength was 355 nm, the repetition frequency was 10 Hz, and the energy was 35 mJ / pulse; after the substrate was heated to 600 °C, the antiferromagnetic layer was deposited under an oxygen pressure of 3 × 10⁻⁶ mJ / pulse. -2 Thin film deposition was performed at Pa to obtain an antiferromagnetic NiO layer with a thickness of 40 nm.

[0069] (4) Fabrication of nonferromagnetic layers using molecular beam epitaxy: The vacuum level of the molecular beam epitaxy growth cavity is maintained at 10. - 10 In the Torr ultra-high vacuum chamber, evaporation sources Pt and Te are installed. The evaporation rate is determined by a film thickness monitoring instrument (FDC) to control the flux ratio during the growth process. After the substrate temperature reaches 600°C, annealing is performed for 60 min, and then the substrate temperature is reduced to 300°C for growth. The evaporation rate of the Pt evaporation source is 0.5 nm / min, and the evaporation rate of the Te evaporation source is 1.5 nm / min. The thickness of the resulting non-ferromagnetic layer PtTe2 is 15 nm.

[0070] A schematic diagram of the spin terahertz emission device prepared in this embodiment is shown below. Figure 1 As shown. When the spin terahertz emitting device prepared in this embodiment is placed in a variable-temperature (0-300K) terahertz time-domain spectroscopy system, it can emit terahertz waves under conditions without an external magnetic field, and the emission efficiency is high.

[0071] Comparative Example 1

[0072] Terahertz emission devices with ferromagnetic / non-ferromagnetic heterojunction structures require an external magnetic field and cannot achieve terahertz emission without a field strength.

[0073] Comparative Example 2

[0074] Terahertz emission devices with ferromagnetic / non-ferromagnetic / ferromagnetic heterojunction structures require an external magnetic field and cannot achieve terahertz emission without a field strength.

[0075] Comparative Example 3

[0076] Terahertz emission devices with antiferromagnetic (single crystal) / nonferromagnetic heterojunction structures have extremely low emission efficiency.

[0077] As can be seen from the test results of the embodiments and comparative examples, the spin terahertz emission device provided by the present invention can realize field-free spin terahertz emission with high emission efficiency; moreover, it can achieve wide-bandwidth, high-efficiency spin terahertz radiation in the range of 0 to 300K.

[0078] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A spin terahertz emission device, comprising a ferromagnetic material layer, an anti-ferromagnetic layer and a non-ferromagnetic layer which are sequentially stacked; the ferromagnetic material layer is composed of a two-dimensional ferromagnetic material or a ferromagnetic metal; the two-dimensional ferromagnetic material is Fex GeTe2 or CrTe2, wherein x is 3-5 in Fex GeTe2; the ferromagnetic metal is composed of Co, Fe or Ni; the anti-ferromagnetic layer is composed of NiO or CrSb; The non-ferromagnetic layer has a composition of a topological insulator, a topological semimetal, or a heavy metal; the topological insulator is Bi2Se3, Bi2Te3, Bi x Sb 1-x , Sb2Te3, or (Bi x Sb 1-x )2Te3. Bi x Sb 1-x x is 0-1; (Bi x Sb 1-x )2Te3x is 0-1; the topological semimetal is PtTe2 or WTe2.

2. The spin terahertz emission device of claim 1, wherein, The thickness of the spin terahertz emission device is 25-130 nm.

3. The spin terahertz emission device of claim 1, wherein, The thickness of the ferromagnetic material layer is 2-10 nm.

4. The spin terahertz emission device of claim 1, wherein, The thickness of the anti-ferromagnetic layer is 10-100 nm.

5. The spin terahertz emission device of claim 1, wherein, The thickness of the non-ferromagnetic layer is 2-15 nm.

6. A method of producing a spin terahertz emission device as claimed in any one of claims 1 to 5, comprising the steps of: The ferromagnetic material layer, the anti-ferromagnetic layer and the non-ferromagnetic layer are sequentially prepared on the surface of a substrate to obtain the spin terahertz emission device. 7.Use of the spin terahertz emission device according to any one of claims 1-5 or prepared by the preparation method of claim 6 in field-free spin terahertz emission.

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