RU2392680C2 - Semiconductor ferrimagnetic material - Google Patents

Abstract

FIELD: physics, semiconductors.

SUBSTANCE: invention relates to semiconductor materials based on metal oxides, particularly to homogeneous polycrystalline materials based on complex oxides of the class of diluted magnetic semiconductors. The invention can be used in spintronics. The semiconductor ferromagnetic material has paramagnetic state transition temperature T_k=470-520 K and is a solid solution oxides of zinc, aluminium or gallium, magnesium and iron having formula (ZnAl₂O₄)_1-x(MgFe₂O₄)_x or (ZnGa₂O₄)_1-x(MgFe₂O₄)_x, where x=0.01-0.10.

EFFECT: obtaining thermally stable material.

6 dwg, 3 tbl, 4 ex

Description

The invention relates to materials based on metal oxides, specifically to homogeneous polycrystalline materials based on complex oxides of the class of diluted magnetic semiconductors with semiconductor and ferrimagnetic properties, as well as a high Curie temperature T _K = 470-520 K with thermal stability of the product.

The invention can be used in spintronics - the field of quantum electronics, in which the electron spin is used along with the charge for the physical representation of information, due to the presence of their own mechanical and associated magnetic moments.

The development of spintronics is largely constrained by the lack of suitable materials that satisfy three main criteria:

- preservation in the obtained magnetic semiconductor materials of the structure and physicochemical properties of the original semiconductor matrices without deterioration of their consumer characteristics;

- conservation of magnetic orientation in semiconductors with n- and p-movable current carriers at temperatures well above room temperature;

- simplicity and reliability of methods for the synthesis of materials, the possibility of their structural inclusion in standard semiconductor circuits.

Magnetic semiconductor materials are usually divided into the following classes: Concentrated Magnetic Semiconductors (CMC); Semi-Magnetic Semiconductors (PMP); Inhomogeneous Magnetic Materials (NMM); High-Temperature Ferromagnetic Semiconductors (VTFP) and Diluted Magnetic Semiconductors (RMP) [V.A. Ivanov et al. Spintronics and spintronic materials. Russian Academy of Sciences, Chemical Series, 2004, No. 11, 2255-2303].

CMPs, which include EuO, Cr-chalcogenide spinels MeCr ₂ Xal ₄ , complex oxides BiMnO ₃ , CeCuO ₃ , YTiO ₃ , and pnictides Mn (Cr) As (Sb), have not received practical application due to the low Curie temperatures and purity technological requirements for electronic materials. The same reasons, plus instability, impede the practical use of the PMF obtained on the basis of the matrices A ^II B ^VI and A ^IV B ^VI (A ^II - Zn, Cd, Hg; A ^IV - Pb, Sn; B ^VI - S, Se, Te), CdMnSe, PbSnMnTe, in which the transition metal ions Fe ²⁺ , Mn ^2+, or Co ²⁺ randomly replace the A elements at the sites of the crystal lattice.

HMMs are composite materials containing oxides of TiO ₂ , ZnO and particles of magnetic metals Fe, Co and Ni. The disadvantage of such mixtures is their non-phase and irreproducibility of magnetic characteristics. Heterogeneity of NMM is shown by the example of composites based on zinc and cobalt oxides Zn _1-X Co ²⁺ _X O, for which ferromagnetism is due to the presence of cobalt clusters [Jae Hyun Kim et al., Magnetic properties of epitaxially grown semiconducting Zn _1-X Co _X O thin films by pulsed laser deposition. J. Appl. Phys., 2002, v. 92, No. 10, p. 6066-6071], [R. Rode et al., Magnetic semiconductors based on cobalt substituted ZnO. J. Appl. Phys., 2003, v. 93, No. 10, p. 7676-7678].

HTFs are CdGeP ₂ : Mn ₂ , ZnGeP ₂ : Mn, CdGeAs ₂ : Mn, ZnSiGeN ₂ : Mn materials with an averaged Mn / Cd or Zn≤20% ratio and transition temperatures to the paramagnetic state of 300-350 K. The disadvantage of such materials is the mismatch of the physicochemical characteristics of the WTPP with the initial semiconductor matrices and insufficiently high Curie temperatures.

Of particular interest is the class of diluted magnetic semiconductors. This class includes materials in which III-V (III — Al, Ga, In; V — P, As, Sb) or II-IV (II — Zn, Cd; IV — Si, Ge, Pb, Sn), in which the atoms of metals of groups II, III, and IV are statistically replaced by transition metal atoms with unfilled 3d-electron shells. Among the most studied RMPs are Ga _1-x Mn _x As material with x≤9-10 wt.% The paramagnetic transition temperature up to 172 K [AMNazmul, S. Sugahara and M. Tanaka, Phys. Rev., V, 2003 , V.67]. The disadvantage of these RMPs is that the Curie temperatures are not high enough. The second drawback is the presence of toxic arsenic and gallium in the composition of the RMP, which is incompatible with the main material of microelectronics - silicon.

Closest to the claimed material is a diluted ferrimagnetic semiconductor composition (ZnGa ₂ O ₄ ) _0.85 (Fe ₃ O ₄ ) _0.15 [ASRisbud et.al., Dilute ferromagnetic semiconductors in Fe-substituted spinel ZnGa ₂ O ₄ J.Phys .Condens.Matter 17 (2005), p. 1003-1010].

The disadvantages of the ferrimagnetic semiconductor composition (ZnGa ₂ O ₄ ) _0.85 (Fe ₃ O ₄ ) _0.15 include the fact that the material is characterized by an insufficiently high Curie temperature (T _K close to 200 K) and a large band gap (4.1 eV ) The second disadvantage is the inhomogeneity of the material, which limits its use.

The invention is directed to the creation of a homogeneous oxide material of the RMP class, which has semiconductor and ferrimagnetic properties with a transition temperature to the paramagnetic state T _K = 470-520 K. By ferrimagnetic is meant the state of the material in which the orientation of the spins of magnetic ions of different magnetic sublattices is antiparallel. At the same time, the sublattices themselves have magnetic moments of different magnitude, so that the total magnetization in the magnetically ordered state is nonzero.

The technical result is achieved by the fact that a homogeneous semiconductor ferrimagnetic material is proposed, characterized by a transition temperature to the paramagnetic state T _K = 470-520 K, which is a solid solution of oxides of zinc, aluminum, magnesium and iron, corresponding to the formula:

(ZnAl ₂ O ₄ ) _1-x (MgFe ₂ O ₄ ) _x , where

x = 0.01 ÷ 0.10;

or a solid solution of oxides of zinc, gallium, magnesium and iron, corresponding to the formula:

(ZnGa ₂ O ₄ ) _1-x (MgFe ₂ O ₄ ) _x , where

x = 0.01 ÷ 0.10.

The values of x are chosen for reasons that for x <0.01 ferrimagnetic properties are not manifested, and for x> 0.10, the solid solution loses homogeneity.

The invention consists in the following.

The semiconductor ferrimagnetic material according to the invention is a solid solution consisting of oxides of zinc, aluminum, magnesium and iron, or of oxides of zinc, gallium, magnesium and iron.

The invention is illustrated by the following accompanying drawings and tabular data.

Figure 1. Temperature dependences of the specific magnetization (σ) of the material using the example of (ZnAl ₂ O ₄ ) _0.96 (MgFe ₂ O ₄ ) _0.04 .

Figure 2. Temperature dependences of the specific magnetization (σ) of the material using the example of (ZnGa ₂ O ₄ ) _0.96 (MgFe ₂ O ₄ ) _0.04 .

Figure 3. Temperature dependences of the magnetic susceptibility (1 / χ) of the material using the example of (ZnAl ₂ O ₄ ) _0.96 (MgFe ₂ O ₄ ) _0.04 .

Figure 4. Temperature dependences of the magnetic susceptibility (1 / χ) of the material using the example of (ZnGa ₂ O ₄ ) _0.96 (MgFe ₂ O ₄ ) _0.04 .

Figure 5. Diffuse scattering spectra (DR) of photoluminescence (PL) for the material (ZnAl ₂ O ₄ ) _0.96 (MgFe ₂ O ₄ ) _0.04 .

6. Diffuse scattering spectra (DR) of photoluminescence (PL) for the material (ZnGa ₂ O ₄ ) _0.98 (MgFe ₂ O ₄ ) _0.02 .

Table 1 The results of x-ray phase analysis of the material composition (ZnAl ₂ O ₄ ) _0.96 (MgFe ₂ O ₄ ) _0.04 Cubic syngony, F _d3m , a = 8.0995 (16) Å 2θ I / I ₀ d _exp h k l d _calculation Δ2θ 18.9 2 4.6780 one one one 4,67626 -0.007 31,2 82 2,8657 2 2 0 2.86361 -0.024 36.7 one hundred 2.4429 3 one one 2,44210 -0.013 44.7 8 2,0255 four 0 0 2,02488 -0.016 49.0 8 1.8589 3 3 one 1.85816 -0.023 55.5 22 1.6537 four 2 2 1.65331 -0.016 59.2 32 1.5592 3 3 3 1,55875 -0.022 65.1 38 1.4314 four four 0 1.43181 0.019 74.0 6 1,2806 6 2 0 1,28065 0 77,2 eleven 1,2348 5 3 3 1,23517 0.024

table 2 The results of x-ray phase analysis of the material composition (ZnGa ₂ O ₄ ) _0.96 (MgFe ₂ O ₄ ) _0.04 Cubic syngony, F _d3m , a = 8.3422 (15) 2θ I / I ₀ d _exp h k l d _calculation Δ2θ 18.39 6 4.8243 one one one 4.8164 -0.031 30.30 25 2,9497 2 2 0 2,9494 -0.003 35.67 one hundred 2,5170 3 one one 2,5153 -0.026 37.32 13 2,4094 2 2 2 2,4082 -0.020 43.38 22 2,0859 four 0 0 2,0855 -0.007 53.82 13 1.7033 four 2 2 1.7028 -0.016 57.36 42 1,6063 3 3 3 1,6055 -0.034 63.03 fifty 1.4748 four four 0 1.4747 -0.004 66.27 3 1.4103 5 3 one 1.4101 -0.013 71.58 four 1,3182 6 2 0 1.3190 0.051 74.61 13 1.2720 5 3 3 1.2722 0.012 75.63 8 1.2574 6 2 2 1.2576 0.019 79.62 four 1,2041 four four four 1,2041 0.001 87.48 5 1,1150 6 four 2 1,1148 -0.023 Table 3 Curie temperatures for the claimed materials No. of Example The composition of the solid solution Paramagnetic transition temperature T _K (± 10) one (ZnAl ₂ O ₄ ) _0.99 (MgFe ₂ O ₄ ) _0.01 520 2 (ZnAl ₂ O ₄ ) _0.96 (MgFe ₂ O ₄ ) _0.04 520 3 (ZnAl ₂ O ₄ ) _0.90 (MgFe ₂ O ₄ ) _0.10 520 four (ZnGa ₂ O ₄ ) _0.99 (MgFe ₂ O ₄ ) _0.01 470 5 (ZnGa ₂ O ₄ ) _0.96 (MgFe ₂ O ₄ ) _0.04 470 6 (ZnGa ₂ O ₄ ) _0.90 (MgFe ₂ O ₄ ) _0.10 480

The claimed semiconductor material has ferrimagnetic properties, as indicated by the temperature dependence of the specific magnetization and magnetic susceptibility (Figure 1 - Figure 4), which correspond to the declared properties [Koroleva L.I. Magnetic semiconductors. M., publishing house of Moscow State University, 2003, 312 pp.] And allow one to determine the Curie temperature.

The claimed semiconductor ferrimagnetic material has thermal stability, as indicated by the course of the temperature dependence of the specific magnetization (Fig. 1 and Fig. 2) and magnetic susceptibility (Fig. 4) of solid solutions during heating and subsequent cooling.

The semiconductor properties of the claimed material are confirmed by the results of measurements of the band gap based on diffuse scattering and photoluminescence spectra (Figs. 5, 6).

The homogeneity of the material is confirmed by the results of x-ray phase analysis (Table 1, 2).

Table 3 presents examples of the compositions of the claimed semiconductor ferrimagnetic material and the temperature of the transition to the paramagnetic state.

Below are examples of the receipt of the claimed material.

Example 1

Zinc oxide, iron oxide Fe ₂ O ₃ , magnesium hydroxide and aluminum hydroxide containing not less than 99.99% of the basic substance were used as starting materials.

A portion of a powder thoroughly ground under ethanol corresponding to the gross composition of (ZnAl ₂ O ₄ ) _0.99 (MgFe ₂ O ₄ ) _0.01 , obtained from oxides or hydroxides of the corresponding metals, was loaded into a platinum crucible and annealed according to the following scheme: stage - annealing at 1073 K for 10 hours, followed by cooling to room temperature; the second is annealing at 1273 K for 10 hours, followed by cooling to room temperature; the third - annealing at 1473 K also for 10 hours, followed by cooling.

Example 2

As starting materials, zinc oxide, iron oxide Fe ₂ O ₃ , magnesium hydroxide and alumina containing not less than 99.99% of the basic substance were used.

A portion of a powder thoroughly ground under ethanol corresponding to the gross composition of (ZnAl ₂ O ₄ ) _0.96 (MgFe ₂ O ₄ ) _0.04 obtained from oxides or hydroxides of the corresponding metals was loaded into a platinum crucible and annealed according to the following scheme: stage - annealing at 1073 K for 10 hours, followed by cooling to room temperature; the second is annealing at 1273 K for 10 hours, followed by cooling to room temperature; the third - annealing at 1573 K also for 10 hours, followed by cooling.

Example 3

Zinc formate, iron oxide Fe ₂ O ₃ , magnesium hydroxide and alumina containing at least 99.99% of the basic substance were used as starting materials.

A portion of a powder thoroughly ground under ethanol corresponding to the gross composition of (ZnAl ₂ O ₄ ) _0.90 (MgFe ₂ O ₄ ) _0.10 obtained from iron and aluminum oxides, zinc formate and aluminum hydroxide was loaded into a platinum crucible and annealed according to the following scheme: the first stage - annealing at 1073 K for 10 hours, followed by cooling to room temperature; the second is annealing at 1173 K for 10 hours, followed by cooling to room temperature; the third - annealing at 1573 K also for 10 hours, followed by cooling.

Example 4

Zinc oxide, iron oxide Fe ₂ O ₃ , magnesium hydroxide and gallium oxide containing not less than 99.99% of the basic substance were used as starting materials.

A portion of a powder thoroughly ground under ethanol corresponding to the gross composition (ZnGa ₂ O ₄ ) _0.99 (MgFe ₂ O ₄ ) _0.01 obtained from oxides or hydroxides of the corresponding metals was loaded into a platinum crucible and annealed according to the following scheme: stage - annealing at 1073 K for 10 hours, followed by cooling to room temperature; the second is annealing at 1173 K for 10 hours, followed by cooling to room temperature; the third - annealing at 1423 K also for 10 hours, followed by cooling.

The material according to examples No. 5-6 of Table 3 was obtained in a similar way.

The materials presented by illustrations and tabular data were studied by X-ray diffraction (XRD), thermogravimetric (TG) and differential thermal (DTA) analyzes. X-ray diffraction analysis was performed using a DRON-3M diffractometer and a Guinier de Wolff monochromator camera. Only lines characteristic of the semiconductor structures of the materials indicated in Table 1-2 were present on the X-ray diffraction patterns.

TG and DTA analyzes were performed using a TGD 7000 thermal analyzer manufactured by ULVAK SINKU-RIKO, Japan.

According to the TG data, within the instrumental error of the device, the gross composition of the synthesized samples does not differ from the initial gross composition.

DTA curves indicated the absence of phase transitions of the first kind, which indicates the homogeneity of the obtained oxide material.

The dependences of the specific magnetization and magnetic susceptibility of the material were studied by the ponderomotive method [V.I. Chechernikov. Magnetic measurements. Moscow State University, 1969, 388 pp.] In a magnetic field of 0.86 T (8.6 kOe) in the temperature range 77-670 K.

Measurement of the band gap of the material (Fig.5, 6) obtained using the spectra of DR and PL [FMLiu, JHJia, LD Zhang. Appl. Phys. A. Vol.70, No. 4 (2000), pp.457-459], indicate that for the solid solution (ZnAl ₂ O ₄ ) _0.96 (MgFe ₂ O ₄ ) _0.04 , the strongest luminescence with maximum at a wavelength of 430 nm. This corresponds to the band gap in the solid solution in the region of 2.8-2.9 eV. For the solid solution (ZnGa ₂ O ₄ ) _0.98 (MgFe ₂ O ₄ ) _0.02 , the strongest luminescence is observed with a maximum at a wavelength of 550 nm. This corresponds to the band gap in the solid solution in the region of 2.2-2.4 eV.

As can be seen from Figs. 1-6, Tables 1-3 and the above examples, the claimed product is a homogeneous semiconductor ferrimagnetic material of the RMP class with a Curie temperature T _K = 470-520 K. The unique combination of semiconductor and ferrimagnetic properties of the claimed material makes it a promising product for practical use in spintronics.

Claims (1)

A semiconductor ferrimagnetic material characterized by a paramagnetic transition temperature Т _К = 470-520К, which is a solid solution of zinc, aluminum, magnesium and iron oxides corresponding to the formula
(ZnAl ₂ O ₄ ) _1-x (MgFe ₂ O ₄ ) _x ,
or a solid solution of oxides of zinc, gallium, magnesium and iron, corresponding to the formula
(ZnGa ₂ O ₄ ) _1-x (MgFe ₂ O ₄ ) _x , where x = 0.01 ÷ 0.10.

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