CN102956814B - Lanthanum strontium copper manganese sulfur oxygen diluted magnetic semiconductor material and preparation method thereof - Google Patents

Abstract

The invention discloses a lanthanum-strontium-copper-manganese-sulfur dilute magnetic semiconductor material, which has the chemical formula: La _1-x Sr _x Cu _1-y Mn _y SO. The invention also discloses a preparation method of the lanthanum strontium copper manganese disulfide magnetic semiconductor material. The raw materials are mixed, fully ground under the protection of argon, and then stamped under a certain pressure; the obtained compressed tablet is sealed in a vacuum container , placed in a tube furnace to raise the temperature, and then calcined at a constant temperature to obtain a lanthanum strontium copper manganese disulfide magnetic semiconductor material. The present invention adopts the method of replacing Cu ⁺ with Mn ²⁺ to introduce magnetic moments, and then partially replaces La with Sr to introduce hole-type carriers. Through the above doping, the conductivity and magnetic properties of the semiconductor can be well controlled, and Curie is obtained. Diluted magnetic semiconductor with higher temperature ZrCuSiAs structure, the diluted magnetic semiconductor material has a very high ferromagnetic transition temperature, the Curie temperature T _C is increased to 199K, and does not contain highly toxic elements such as As.

Description

A kind of lanthanum strontium copper manganese sulfur oxide dilute magnetic semiconductor material and preparation method thereof

technical field

The invention relates to the field of dilute magnetic semiconductor materials and their preparation, in particular to a lanthanum strontium copper manganese dioxygen dilute magnetic semiconductor material with a relatively high ferromagnetic transition temperature and a preparation method thereof.

Background technique

Diluted Magnetic Semiconductors (DMS) refers to artificially doping a small amount of magnetic atoms into non-magnetic semiconductor materials to obtain magnetic semiconductor materials. Based on this, it is possible to prepare magnetism, light and electricity. New semiconductor electronic devices. Due to the application potential in the field of spintronics, dilute magnetic semiconductors have attracted the attention of many researchers [T.Dietl, A ten-year perspective on dilute magnetic semiconductors and oxides.Nature Materials9, 965-974(2010).] . (Ga, Mn) As, (In, Mn) As, (Ga, Mn) N are typical III-V dilute magnetic semiconductors, replacing Ga or In with Mn can only obtain metastable compounds, and only molecular Beam epitaxy grows a thin film with a certain Mn doping concentration.

Recently, a p-group dilute magnetic semiconductor bulk material Li(Zn, Mn)As was discovered [Z.Deng et al., Nature Communications.2: 422 (2011)], its ferromagnetic transition temperature (ie Curie temperature, Expressed as T _C ) is only 50K, and the arsenic element in it may pollute the environment and is not conducive to large-scale application. Obtaining a dilute magnetic semiconductor material with a higher ferromagnetic transition temperature and being environmentally friendly is a prerequisite for the development of its application.

The non-magnetic semiconductor LaCuSO was first obtained by oxidizing LaCuS ₂ , and its lattice structure was given [M.Palazzi, Acad.Sci., Paris, CR1981, 292, 789]. LaCuOS obtained by the solid-state reaction method is a p-type semiconductor [Y. Takano.; K. Yahagi.; K. Sekizawa. Physica A. 1995, 206 & 207, 764]. LaCuOS is a semiconductor with a wide energy gap, and its energy gap reaches 3.1 eV [Shin-ichiro Inoue, Kazushige Ueda, Hideo Hosono and Noriaki Hamada, Phys. Rev. B64, 245211 (2001)]. It has the same ZrCuSiAs structure as the iron-based superconductor parent LaFeAsO. As a transparent p-type material, LaCuSO is very important to realize transparent pn junctions based on semiconductor materials, and is an attractive candidate material in the field of optoelectronic devices. If the ferromagnetic order is introduced into the wide-gap p-type oxide semiconductor LaCuSO by doping Mn and other magnetic ions, it will be a great impetus to its practical application.

Contents of the invention

Aiming at the problems in the prior art that the ferromagnetic transition temperature (Curie temperature) of the diluted magnetic semiconductor is relatively low and may cause environmental pollution, the present invention provides an environmentally friendly diluted magnetic semiconductor material with a higher Curie temperature.

A lanthanum strontium copper manganese disulfide dilute magnetic semiconductor material, the general chemical formula is:

La _1-x Sr _x Cu _1-y Mn _y SO, wherein x=0-0.1, y=0.05-0.1.

When a small amount of magnetic atoms are doped in a non-magnetic semiconductor material, the originally non-magnetic material becomes magnetic. The present invention introduces magnetic ions Mn ²⁺ into the non-magnetic semiconductor material LaCuSO to replace a part of Cu ⁺ , thereby introducing a magnetic moment, transforming the non-magnetic semiconductor material into a dilute magnetic semiconductor material, and selectively introducing Sr ²⁺ as a substitute crystal Part of the La ³⁺ position in the lattice, thus introducing hole-type carriers, the more Sr atoms doped, the higher the hole concentration and the stronger the conductivity. The holes introduced by Sr doping also enhance the RKKY interaction between the magnetic moments of Mn ²⁺ ions, which is beneficial to increase the ferromagnetic transition temperature. In this way, the original non-magnetic semiconductor material is converted into a dilute magnetic semiconductor material, and the conductivity is also improved.

Since the higher the concentration of Mn ²⁺ , the more magnetic moments in the material, the greater the Sr content, the better the conductivity of the material. Within a certain range of Sr doping concentration, the greater the Sr content, the stronger the interaction between the magnetic moments, and the higher the Curie temperature. However, the solid solubility of Sr in this material is limited. Therefore, preferably, the chemical formula composition is: La _1-x Sr _x Cu _1-y Mn _y SO, wherein x=0.05-0.1, y=0.05-0.1.

The present invention also provides a method for preparing the lanthanum strontium copper manganese disulfide magnetic semiconductor material. First, the raw materials are mixed in proportion and fully reacted, and then compressed under high pressure conditions, and then the compressed tablets are calcined after vacuum and high temperature treatment, and finally the obtained The lanthanum strontium copper manganese dioxygen dilute magnetic semiconductor material.

A preparation method of a lanthanum strontium copper manganese dilute oxygen sulfide magnetic semiconductor material, comprising the following steps:

(1) Fully mix the raw materials La ₂ O ₃ , SrS, La, Cu, S and Mn in proportion, grind them under the protection of argon, and then punch them under a pressure of 450-550 MPa to obtain compressed tablets;

(2) Sealing the pressed tablet in a vacuum container, placing the vacuum container in a tube furnace to raise the temperature, and then calcining at a constant temperature to obtain the lanthanum strontium copper manganese disulfide magnetic semiconductor material.

Preferably, the grinding time is 20-40 minutes; the particles of the reactants are made as fine as possible and mixed uniformly, which accelerates the progress of the solid phase reaction.

Preferably, the vacuum container is a vacuum quartz tube; the vacuum degree in the vacuum quartz tube is better than 0.1Pa. Under vacuum conditions, the reactants are not affected by gases such as oxygen in the air, which reduces the formation of impurities such as oxides to a certain extent.

The temperature raising condition is as follows: the temperature is raised to 1223±50K after 1800-2200 minutes.

The constant temperature calcination condition is: calcination at 1223±50K for 1800-2200min. After the calcination process, the crystal form can be changed, and finally a single-phase polycrystalline block that exists stably in the form of a block is obtained, that is, the lanthanum strontium copper manganese dioxygen dilute magnetic semiconductor material.

The present invention adopts the method of replacing Cu ⁺ with Mn ²⁺ to introduce magnetic moments, and then partially replaces La with Sr to introduce hole-type carriers. Through the above doping, the conductivity and magnetism of the semiconductor can be well controlled, and ferromagnetism is obtained. Diluted magnetic semiconductor with higher transition temperature (Curie temperature) ZrCuSiAs type structure, the diluted magnetic semiconductor material has a very high ferromagnetic transition temperature, the Curie temperature T _C is increased to 199K, and does not contain highly toxic elements such as As. As a new dilute magnetic semiconductor material, the lanthanum strontium copper manganese oxysulfide obtained by the invention has broad application prospects in the fields of spintronics, quantum computing, transparent semiconductors, luminescent materials and the like.

Description of drawings

Fig. 1 is the crystal lattice structure schematic diagram of the present invention lanthanum strontium copper manganese disulfide dilute magnetic semiconductor material La _1-x Sr _x Cu _1-y Mn _y SO;

Fig. 2 is the room temperature powder X-ray diffraction spectrum of La _1-x Sr _x Cu _{1-y Mny} SO (x=0.05, 0.075, 0.1, y=0.075) of the present invention; the inset shows that the lattice constants a and c vary with The change of Sr doping amount x;

Fig. 3 is the curve of the resistivity of La _1-x Sr _x Cu _{1-y Mny} SO (x=0.05, 0.075, 0.1, y=0.075) of the present invention as a function of temperature;

Fig. 4 is the curve of the magnetic susceptibility of La _1-x Sr _x Cu _{1-y Mny} SO (x=0.05, y=0.075) of the present invention as a function of temperature; the illustration shows the variation of magnetization M with magnetic field H when T=2K Variety;

Fig. 5 is the curve of the magnetic susceptibility of La _1-x Sr _x Cu _{1-y Mny} SO (x=0.05, y=0.1) of the present invention as a function of temperature, and the inset is that the magnetization M of the sample changes with T=2K Changes in the magnetic field strength H.

Detailed ways

Example 1

1) _La2O3 , _SrS , La, Cu, S and Mn powder and other raw materials are fully mixed according to the molar ratio of La, Sr, Cu, Mn, S, O and other elements 0.95:0.05:0.925:0.075:1:1, Grinding in an Ar gas protective atmosphere, and then punching under a pressure of about 500MPa to obtain a tablet;

2) The above-mentioned pressed tablet is sealed in a evacuated quartz tube, then put into a tube furnace and heated to 1223K for 2000 minutes, then calcined at 1223K for 2000 minutes, and then cooled to room temperature to obtain a polycrystalline block. The grid structure is shown in Figure 1.

It can be seen from Fig. 2 that the main phase of the sample obtained by the above process is La _0.95 Sr _0.05 Cu _0.925 Mnn _0.075 SO compound (main phase ≥ 99%) with a tetragonal structure (ZrCuSiAs type). Except a small amount*, Except for the SrS, (La, Sr)MnO ₃ , and MnS impurity phases marked with # (the impurity phase content is less than 1%), all X-ray diffraction peaks can be indexed, and the unit cell parameters of the sample are:

It can be seen from Figure 3 that the resistivity is on the order of tens of ohm centimeters at room temperature, and as the temperature decreases, the resistivity drops rapidly, reaching hundreds of ohm centimeters at low temperatures, which is a typical semiconductor behavior. With the increase of Sr doping amount, the resistivity decreases gradually.

It can be seen from Figure 4 that the synthesized lanthanum strontium copper manganese sulfur oxide dilute magnetic semiconductor material has good ferromagnetic properties: its ferromagnetic transition temperature T _C has reached 180K, exceeding the dilute magnetic semiconductor material that has been publicly reported so far The highest ferromagnetic transition temperature of the bulk material, and it can be seen from the illustration that the saturation magnetic moment reaches 0.79μB/Mn when H=5kOe, indicating that lanthanum strontium copper manganese sulfoxide is a new type of dilute magnetic semiconductor material. Huge application advantages.

Example 2

1) _La2O3 , _SrS , La, Cu, S and Mn powder and other raw materials are fully mixed according to the molar ratio of La, Sr, Cu, Mn, S, O and other elements 0.95:0.05:0.9:0.1:1:1, Grinding in an Ar gas protective atmosphere, and then punching under a pressure of about 500MPa to obtain a tablet;

2) Seal the above-mentioned pressed tablet in a vacuumized quartz tube, then put it into a tube furnace and heat up to 1273K for 2000 minutes, then calcined at 1273K for 2000 minutes, and then cooled to room temperature to obtain a polycrystalline block. The grid structure is shown in Figure 1.

The main phase of the sample obtained by the above process is La _0.95 Sr _0.05 Cu _0.9 Mn _0.1 SO with a tetragonal structure. It can be seen from Figure 5 that the synthesized La _0.95 Sr _0.05 Cu _0.9 Mn _0.1 SO dilute magnetic semiconductor material has good ferromagnetic properties: its ferromagnetic transition temperature T _C reaches 157K, and it can be seen from the illustration It is shown that the saturation magnetic moment reaches 1.06μ _B /Mn when H=5kOe, indicating that lanthanum strontium copper manganese oxysulfide, as a new type of dilute magnetic semiconductor material, has advantages in practical applications.

Example 3-7

Table 1 shows the raw material ratio, calcination temperature, ferromagnetic transition temperature and unit cell parameters of La _1-x Sr _x Cu _1-y Mn _y SO (x=0-0.1, y=0.05-0.1) samples.

Table 1

Among them, the sample La _0.9 Sr _0.1 Cu _0.925 Mn _0.075 SO obtained in Example 6 contains a small amount of other ferromagnetic impurity phases, so the ferromagnetic transition temperature of the main phase is difficult to accurately determine, which is about 210K.

Claims (6)

1. A lanthanum-strontium-copper-manganese-oxygen-diluted magnetic semiconductor material, characterized in that the chemical formula is: La _1-x Sr _x Cu _1-y Mn _y SO, wherein x=0-0.1, y=0.05-0.1. 2. The lanthanum strontium copper manganese dioxygen dilute magnetic semiconductor material according to claim 1, characterized in that the chemical formula is: La _1-x Sr _x Cu _1-y Mn _y SO, wherein x=0.05～0.1, y =0.05～0.1. 3. The preparation method of the lanthanum strontium copper manganese sulfur oxide dilute magnetic semiconductor material according to claim 1 or 2, is characterized in that, comprises the steps: (1) Fully mix the raw materials La ₂ O ₃ , SrS, La, Cu, S and Mn in proportion, grind them under the protection of argon, and then punch them under a pressure of 450-550 MPa to obtain tablets; (2) sealing the pressed tablet in a vacuum container, placing the vacuum container in a tube furnace to raise the temperature, and then calcining at a constant temperature to obtain the lanthanum strontium copper manganese disulfide magnetic semiconductor material; The temperature raising condition is: heating to 1173~1273K after 1800~2200min; The constant temperature calcining condition is: calcining at 1173-1273K for 1800-2200min. 4. The method for preparing the lanthanum strontium copper manganese dioxygen disulfide magnetic semiconductor material according to claim 3, characterized in that the grinding time is 20-40 min. 5. The preparation method of the lanthanum strontium copper manganese dioxygen disulfide magnetic semiconductor material according to claim 3, characterized in that the vacuum container is a vacuum quartz tube. 6. The preparation method of the lanthanum strontium copper manganese dioxygen dilute magnetic semiconductor material according to claim 3, characterized in that the vacuum in the vacuum quartz tube is better than 0.1Pa.