CN105084330A - Ferromagnetic semiconductor material Li (Cd, Mn) P and preparation method thereof - Google Patents

Abstract

The present invention provides a ferromagnetic semiconductor material having the formula of Liy (Cd1-xMnx) P, wherein y is greater than 0.6 and less than 1.4, and x is greater than 0 and less than 0.4. The present invention also provides a preparation method of the ferromagnetic semiconductor material, the Liy (Cd1-xMnx) P is prepared by sintering a precursor in an oxygen-isolated environment by solid phase reaction method, wherein y is greater than 0.6 and less than 1.4, x is greater than 0 and less than 0.4, and the sintering temperature is 550-950 DEG C.

Description

A kind of ferromagnetic semiconductor material Li(Cd,Mn)P and preparation method thereof

technical field

The invention relates to a ferromagnetic semiconductor material based on group I-II-V semiconductor materials, in particular to a ferromagnetic semiconductor material with a general chemical structure formula of Li(Cd,Mn)P.

Background technique

Ferromagnetic dilute magnetic semiconductors are realized by doping magnetic ions into the semiconductor. Due to the application prospects of spintronic devices, ferromagnetic dilute magnetic semiconductor systems have been extensively studied as early as the 1990s (Zutic, I. et al., Rev. Mod. Phys. 76, 323, 2004). So far, the most widely studied is the dilute magnetic semiconductor based on the III-V group, that is, the semiconductor with the compound of the group III element and the V element as the parent phase (Ohno, H., Science281, 951, 1998). However, III-V dilute magnetic semiconductors also have problems such as manufacturing process and binding of carriers and magnetic moments.

The recently reported ferromagnetic dilute magnetic semiconductor Li(Zn, Mn)As based on I-II-V semiconductor materials has successfully solved the problem of carrier and magnetic moment binding (Deng, Z. et al., Nature Communications2: 422, 2011), in which the carriers and magnetic moments are provided by Li ions and Mn ions, respectively, which facilitates the study of the mechanism of ferromagnetic semiconductors.

Practical semiconductor materials require controllable carrier types and concentrations, so that desired materials can be obtained through doping. One of the most important applications is to combine electron doped semiconductors and hole doped semiconductors to form the basic unit PN junction of transistors. However, the carrier concentration of Li(Zn,Mn)As is about 10 ¹⁹ -10 ²⁰ cm ^-3 , and its conduction behavior shows strong metallicity. This means that it will be difficult to change its carrier type, and it will not be possible to obtain a PN junction.

In addition, Li(Zn,Mn)As contains toxic element As, which is likely to cause physical damage to personnel during the use and manufacture of materials.

Contents of the invention

Therefore, the object of the present invention is to overcome the defects of the above-mentioned prior art, and provide a ferromagnetic dilute magnetic semiconductor based on I-II-V semiconductor materials, which has stronger semiconductivity, and the carrier type and concentration can be adjusted more easily. , and does not contain the toxic element As.

The invention provides a ferromagnetic semiconductor material whose chemical formula is Li _y (Cd _1-x Mn _x )P, wherein 0.6<y<1.4, 0<x<0.4.

According to the ferromagnetic semiconductor material provided by the present invention, the crystal structure of the ferromagnetic semiconductor material belongs to the cubic crystal system.

The present invention also provides a method for preparing the above-mentioned ferromagnetic semiconductor material, using a solid-state reaction method to sinter the precursor in an environment isolated from oxygen to form Li _y (Cd _1-x Mn _x )P, wherein 0.6<y< 1.4, 0<x<0.4, wherein the substance of the precursor is selected from the group consisting of the following substances: Li, Cd, Mn, P, Li ₃ P, CdP, MnP, wherein the content of each substance meets the iron content to be prepared The ratio of various elements in the magnetic semiconductor material Li _y (Cd _1-x Mn _x )P, wherein the sintering temperature is 550-950°C.

According to the method provided by the present invention, wherein the sintering process is carried out under normal pressure, and the sintering temperature is 600-900°C.

According to the method provided by the present invention, wherein the sintering process is carried out at a pressure higher than one atmospheric pressure, and the sintering temperature is 550-950°C.

According to the method provided by the present invention, wherein the pressure is 1-20GPa.

According to the method provided by the present invention, wherein the precursor includes Li, Cd, Mn, P.

According to the method provided by the present invention, wherein the precursor includes Li ₃ P, Cd, Mn, P, CdP, MnP.

According to the method provided by the present invention, wherein the sintering process is carried out in an inert gas.

According to the method provided by the present invention, wherein the sintering process is carried out in a vacuum environment.

The ferromagnetic semiconductor Li(Cd,Mn)P provided by the present invention no longer contains the toxic element As, and because the electronegativity of the P element is higher than that of the As element, and the electropositivity of the Cd element is stronger than that of the Zn element, the Li (Cd,Mn)P has good semiconductor properties, and the carrier concentration is easier to adjust, so it can be well used in various devices such as spintronic devices.

Description of drawings

Embodiments of the present invention will be further described below with reference to the accompanying drawings, wherein:

Fig. 1 is a schematic diagram of the crystal structure of the ferromagnetic semiconductor provided by the present invention;

Fig. 2 is the graph that the resistivity of Li _0.6 Cd _0.9 Mn _0.1 P in embodiment 1 changes with temperature;

Fig. 3 is the X-ray _{diffraction pattern} of _{Li0.6Cd0.9Mn0.1P} in embodiment 1;

Fig. 4 is the curve graph of the DC magnetic susceptibility of Li _0.6 Cd _0.9 Mn _0.1 P in Example 1 as a function of temperature;

Fig. 5 is the graph that the resistivity of Li _1.4 Cd _0.6 Mn _0.4 P in embodiment 2 changes with temperature;

Fig. 6 is the X-ray diffraction pattern of Li _1.4 Cd _0.6 Mn _0.4 P in embodiment 2;

Fig. 7 is the curve graph of the DC magnetic susceptibility of Li _1.4 Cd _0.6 Mn _0.4 P in Example 2 as a function of temperature;

Fig. 8 is a graph showing the resistivity of Li _1.2 Cd _0.95 Mn _0.05 P in Example 3 as a function of temperature;

Fig. 9 is the X-ray diffraction pattern of Li _1.2 Cd _0.95 Mn _0.05 P in embodiment 3;

Fig. 10 is a graph showing the variation of DC magnetic susceptibility with temperature of Li _1.2 Cd _0.95 Mn _0.05 P in Example 3;

Fig. 11 is a graph showing the resistivity of Li _1.1 Cd _0.9 Mn _0.1 P in Example 4 as a function of temperature;

Figure 12 is the X-ray diffraction pattern of Li _1.1 Cd _0.9 Mn _0.1 P in Example 4;

Fig. 13 is a graph showing the DC magnetic susceptibility of Li _1.1 Cd _0.9 Mn _0.1 P as a function of temperature in Example 4;

Fig. 14 is a graph showing the resistivity of Li _0.6 Cd _0.8 Mn _0.2 P in Example 5 as a function of temperature;

Figure 15 is the X-ray diffraction pattern of Li _0.6 Cd _0.8 Mn _0.2 P in Example 5;

Fig. 16 is a graph showing the DC magnetic susceptibility of Li _0.6 Cd _0.8 Mn _0.2 P as a function of temperature in Example 5;

Fig. 17 is a graph showing the resistivity of Li _1.4 Cd _0.6 Mn _0.4 P as a function of temperature in Example 6;

Figure 18 is the X-ray diffraction pattern of Li _1.4 Cd _0.6 Mn _0.4 P in Example 6;

Fig. 19 is a graph showing the DC magnetic susceptibility of Li _1.4 Cd _0.6 Mn _0.4 P as a function of temperature in Example 6;

Fig. 20 is a graph showing the resistivity of Li _1.05 Cd _0.7 Mn _0.3 P as a function of temperature in Example 7;

Figure 21 is the X-ray diffraction pattern of Li _1.05 Cd _0.7 Mn _0.3 P in Example 7;

Fig. 22 is a graph of the DC magnetic susceptibility of Li _1.05 Cd _0.7 Mn _0.3 P in Example 7 as a function of temperature.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The present invention provides a ferromagnetic semiconductor material based on group I-II-V semiconductor materials, whose general chemical structure is Li _y (Cd _1-x Mn _x )P, wherein 0.6<y<1.4, 0<x< 0.4, x, y represent atomic percent content. The crystal structure of Li _y (Cd _1-x Mn _x )P is shown in Figure 1. It has a space symmetry group of F-43m and belongs to the cubic crystal system. The range of lattice constants is:

Example 1

This embodiment provides a method for preparing a ferromagnetic semiconductor material, including:

1) In a glove box filled with an inert gas, high-purity Li block, Cd powder, Mn powder, and P powder are used according to a predetermined ratio (Li _0.6 Cd _0.9 Mn _0.1 P, the masses are respectively 0.21 grams of Li block, 5.06 grams of Cd powder, Mn powder 0.27 gram, P powder 1.55 gram) evenly mixes, and mixture is packed in alumina ceramic test tube;

2) Vacuum-encapsulate the ceramic test tube with the sample in the quartz tube;

3) The quartz tube was sintered in a high-temperature furnace at 600°C for 20 hours, and Li _0.6 Cd _0.9 Mn _0.1 P was obtained after sintering.

The resistivity of the sample obtained by the method of this embodiment varies with temperature as shown in FIG. 2 , showing good semiconductor properties. The X-ray diffraction pattern of the sample is shown in Figure 3, all the diffraction peaks can find the corresponding diffraction index, indicating that the method provided in this example has prepared a ferromagnetic semiconductor material Li _0.6 Cd _0.9 Mn with high purity and good crystallinity _0.1 p. The relationship between the direct current susceptibility and temperature of the sample is shown in Figure 4, and the ferromagnetic transition temperature is 12K.

Example 2

This embodiment provides a method for preparing a ferromagnetic semiconductor material, including:

1) In a glove box filled with an inert gas, the high-purity Li block, Cd powder, Mn powder, and P powder are used according to a predetermined ratio (Li _1.4 Cd _0.6 Mn _0.4 P, the masses are respectively 0.49 grams of Li block, 3.37 grams of Cd powder, Mn powder 1.10 gram, P powder 1.55 gram) evenly mixes, and mixture is packed in alumina ceramic test tube;

2) Vacuum seal the ceramic test tube with the sample in the quartz tube, and fill a certain amount of inert gas into the quartz tube;

3) The quartz tube was sintered in a high-temperature furnace at a temperature of 900° C. for 5 hours, and Li _1.4 Cd _0.6 Mn _0.4 P was obtained after sintering.

The resistivity of the sample obtained by the method of this embodiment varies with temperature as shown in FIG. 5 , showing good semiconductor properties. The X-ray diffraction pattern of the sample is shown in FIG. 6 , and all the diffraction peaks can be found with corresponding diffraction indices, indicating that the ferromagnetic semiconductor material prepared by the method provided in this example has high purity and good crystallinity. The relationship between the direct current susceptibility and temperature of the sample is shown in Figure 7, and the ferromagnetic transition temperature is 25K.

Example 3

This embodiment provides a method for preparing a ferromagnetic semiconductor material, including:

1) In a glove box filled with an inert gas, high-purity Li ₃ P, P, Cd, Mn, CdP, and MnP are mixed according to a predetermined ratio (Li _1.2 Cd _0.95 Mn _0.05 P, the mass is 1.24 grams of Li ₃ P, P0 .20 gram, Cd3.37 gram, Mn0.20 gram, CdP3.87 gram, MnP0.21 gram) evenly mix, the mixture is packed into niobium tube, and niobium tube is sealed under the protection of inert gas;

2) Vacuum-encapsulate the niobium tube in the quartz tube;

3) The quartz tube was sintered in a high-temperature furnace at a temperature of 750° C. for 15 hours, and Li _1.2 Cd _0.95 Mn _0.05 P was obtained after sintering.

The resistivity of the sample obtained by the method of this embodiment varies with temperature as shown in FIG. 8 , showing good semiconductor properties. The X-ray diffraction pattern of the sample is shown in FIG. 9 , and all diffraction peaks can be found with corresponding diffraction indices, indicating that the ferromagnetic semiconductor material prepared by the method provided in this example has high purity and good crystallinity. The relationship between the DC magnetic susceptibility and temperature of the sample is shown in Figure 10, and the ferromagnetic transition temperature is 28K.

Example 4

This embodiment provides a method for preparing a ferromagnetic semiconductor material, including:

1) In a glove box filled with an inert gas, high-purity Li ₃ P, P, Cd, Mn, CdP, and MnP are mixed according to a predetermined ratio (Li _1.1 Cd _0.9 Mn _0.1 P, the mass is Li ₃ P1.14 grams, P0 .25 gram, Cd3.03 gram, Mn0.16 gram, CdP3.87 gram, MnP0.26 gram) evenly mix, mixture is packed into niobium tube, and under the protection of inert gas, niobium tube is sealed;

2) Vacuum-encapsulate the niobium tube in the quartz tube;

3) Sintering the quartz tube at a temperature of 750° C. in a high-temperature furnace for 20 hours;

4) After the sintering is completed, the obtained sample is ground and mixed under the protection of an inert gas and pressed into tablets, the mixture is put into a niobium tube, and the niobium tube is sealed under the protection of an inert gas;

5) vacuum-encapsulate the niobium tube in the quartz tube;

6) Sintering the quartz tube in a high-temperature furnace at a temperature of 750° C. for 20 hours to obtain Li _1.1 Cd _0.9 Mn _0.1 P.

The resistivity variation behavior with temperature of the sample provided in this embodiment is shown in FIG. 11 , showing good semiconductor properties. The X-ray diffraction pattern of the sample is shown in FIG. 12 , and all the diffraction peaks can be found with corresponding diffraction indices, indicating that the ferromagnetic semiconductor material prepared by the method provided in this example has high purity and good crystallinity. The relationship between the direct current susceptibility and temperature of the sample is shown in Figure 13, and the ferromagnetic transition temperature is 30K.

Example 5

This embodiment provides a method for preparing a ferromagnetic semiconductor material, including:

1) In a glove box filled with an inert gas, the high-purity Li block, Cd powder, Mn powder, and P powder are used according to a predetermined ratio (Li _0.6 Cd _0.8 Mn _0.2 P, and the masses are respectively 0.025 grams of Li block, 0.540 grams of Cd powder, Mn powder 0.066 gram, P powder 0.186 gram) evenly mix, pack into high pressure assembly;

2) Put the high-pressure assembly into a high-pressure device for high-pressure sintering. The sintering program is to slowly increase the pressure to 1GPa at room temperature, then start the heating program to heat to 550°C, keep it at high temperature and high pressure for 2 hours, then drop to room temperature, and then release the pressure to obtain Li _0.6 Cd _0.8 Mn _0.2 P.

The resistivity of the sample obtained by the method of this embodiment varies with temperature as shown in FIG. 14 , showing good semiconductor properties. The X-ray diffraction pattern of the sample is shown in Figure 15, and all the diffraction peaks can be found with corresponding diffraction indices, which shows that the ferromagnetic semiconductor material prepared by the method provided in this example has high purity and good crystallinity. The relationship curve of DC magnetic susceptibility and temperature of the sample is shown in Fig. 16, and the ferromagnetic transition temperature is 13K.

Example 6

This embodiment provides a method for preparing a ferromagnetic semiconductor material, including:

1) In a glove box filled with an inert gas, high-purity Li ₃ P, P, Cd, Mn, CdP, and MnP are mixed according to a predetermined ratio (Li _1.4 Cd _0.6 Mn _0.4 P, the mass is Li ₃ P0.145 grams, P0 .025 gram, Cd 0.202 gram, Mn 0.099 gram, CdP 0.258 gram, MnP 0.052 gram) evenly mix, pack into high pressure assembly;

2) Put the high-pressure assembly into the high-pressure device for high-pressure synthesis. The sintering program is to slowly increase the pressure to 8GPa at room temperature, then start the heating program to heat to 950°C, keep the temperature at high temperature and high pressure for 0.1 hour, then drop to room temperature, and then release the pressure to obtain Li _1.4 Cd _0.6 Mn _0.4 P.

The resistivity of the sample obtained by the method of this embodiment varies with temperature as shown in FIG. 17 , showing good semiconductor properties. The X-ray diffraction pattern of the sample is shown in Figure 18, and all the diffraction peaks can be found with corresponding diffraction indices, indicating that the ferromagnetic semiconductor material prepared by the method provided in this example has high purity and good crystallinity. The relationship curve of DC magnetic susceptibility and temperature of the sample is shown in Figure 19, and the ferromagnetic transition temperature is 8K.

Example 7

This embodiment provides a method for preparing a ferromagnetic semiconductor material, including:

1) In a glove box filled with an inert gas, high-purity Li ₃ P, P, Cd, Mn, CdP, and MnP were mixed according to a predetermined ratio (Li _1.05 Cd _0.7 Mn _0.3 P, the masses were Li ₃ P0.109 g, P0 .028 gram, Cd0.236 gram, Mn0.049 gram, CdP0.301 gram, MnP0.077 gram) evenly mix, pack into high pressure assembly;

2) Put the high-pressure assembly into the high-pressure device for high-pressure synthesis. The sintering program is to slowly increase the pressure to 20GPa at room temperature, then start the heating program to heat to 700°C, keep the temperature at high temperature and high pressure for 1 hour, then drop to room temperature, and then release the pressure;

3) Grinding and mixing the obtained sample under the protection of an inert gas, and repacking it into a high-pressure assembly;

4) Put the high-pressure assembly into the high-pressure device for high-pressure synthesis. The sintering procedure is to slowly increase the pressure to 20GPa at room temperature, then start the heating program to heat to 700°C, keep the temperature at high temperature and high pressure for 1 hour, then cool down to room temperature, and then release the pressure to obtain Li _1.05 Cd _0.7 Mn _0.3 P.

The resistivity of the sample obtained by the method of this embodiment varies with temperature as shown in FIG. 20 , showing good semiconductor properties. The X-ray diffraction pattern of the sample is shown in Figure 21, and all the diffraction peaks can be found with corresponding diffraction indices, indicating that the ferromagnetic semiconductor material prepared by the method provided in this example has high purity and good crystallinity. The relationship curve of DC magnetic susceptibility and temperature of the sample is shown in Figure 22, and the ferromagnetic transition temperature is 12.5K.

The above-mentioned various embodiments have successfully synthesized the ferromagnetic semiconductor material Li _y (Cd _1-x Mn _x )P, 0.6 <y<1.4,0<x<0.4. The proportions of various substances in the precursors used in the methods provided in the above-mentioned embodiments are only exemplary, and are not intended to limit the scope of protection of the present application. Those skilled in the art can easily synthesize Li The specific x and y values in _y (Cd _1-x Mn _x )P determine the weight ratios of the various substances in the precursor.

The mixture of simple substance Li, simple substance Cd, simple substance Mn and simple substance P is used as the precursor in the above-mentioned examples 1, 2 and 5, and the precursor used in the examples 3, 4, 6 and 7 includes the compounds Li ₃ P, CdP , MnP, all successfully synthesized the ferromagnetic semiconductor material Li _y (Cd _1-x Mn _x )P according to the present invention.

According to other embodiments of the present invention, the precursors used in the solid phase method of synthesizing ferromagnetic semiconductor material Li _y (Cd _1-x Mn _x )P are Li source material, Cd source material, Mn source material, P source material mixture. The Li source material, the Cd source material, the Mn source material, and the P source material may be simple substances or compounds, such as Li ₃ P, CdP, and MnP.

According to other embodiments of the present invention, the container containing the precursor is not limited to the alumina ceramic test tube, niobium tube, etc. used in the above embodiments, and may also be in other corrosion-resistant containers, such as BN tubes.

According to other embodiments of the present invention, the way in which the precursor is contained in the sintering process is not limited to the method provided in the above-mentioned embodiments, it only needs to meet the requirement that the precursor is sintered in an environment isolated from oxygen, for example, in an inert gas environment. Sintering under protection, or sintering in a vacuum environment.

According to other embodiments of the present invention, the temperature for forming the ferromagnetic semiconductor material Li _y (Cd _1-x Mn _x )P by atmospheric pressure sintering is preferably 600-900° C., and the sintering time is preferably more than 5 hours.

According to other embodiments of the present invention, the temperature for forming the ferromagnetic semiconductor material Li _y (Cd _1-x Mn _x )P by high pressure sintering is preferably 550-950°C, the sintering time is preferably 0.1 hour or more, and the sintering pressure is higher than one atmospheric pressure , preferably 1-20GPa.

According to other embodiments of the present invention, the sintering process under normal pressure and high pressure is preferably secondary sintering as in Embodiments 4 and 7, or multiple times of sintering.

The ferromagnetic semiconductor material provided by the invention has a ferromagnetic transition temperature of about 30K or less, and the material with a specific composition has a ferromagnetic transition temperature of 30K, and the material exhibits good semiconductivity in the whole temperature range.

In the ferromagnetic semiconductor material provided by the present invention, Cd and P are used to replace Zn and As in Li(Zn,Mn)As respectively, because the electropositive property of Cd element is stronger than that of Zn element, and the electronegativity of P element is higher than As The higher the element, the more semiconducting material Li(Cd,Mn)P is obtained. It makes it easier to adjust the carrier type and concentration in Li(Cd,Mn)P, which provides a guarantee for the application of the material. It is worth mentioning that Li(Cd,Mn)P does not contain the toxic element As, which is an environmentally friendly material.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than limit them. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent replacements to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all of them should be included in the scope of the present invention. within the scope of the claims.

Claims (10)

1. a ferromagnetic semiconductor material, its chemical formula is Li _y(Cd _1-xmn _x) P, wherein 0.6<y<1.4,0<x<0.4.

2. ferromagnetic semiconductor material according to claim 1, the crystalline structure of wherein said ferromagnetic semiconductor material belongs to isometric system.

3. prepare a method for ferromagnetic semiconductor material as claimed in claim 1, utilize solid reaction process, in the environment of isolating with oxygen, sinter precursor, form Li _y(Cd _1-xmn _x) P, wherein 0.6<y<1.4,0<x<0.4,

The material of wherein said precursor is selected from the group of following material formation: Li, Cd, Mn, P, Li ₃p, CdP, MnP, wherein the content of various material meets ferromagnetic semiconductor material Li to be prepared _y(Cd _1-xmn _x) proportioning of various element in P, wherein sintering temperature is 550-950 DEG C.

4. method according to claim 3, wherein said sintering process is carried out at ambient pressure, and sintering temperature is 600-900 DEG C.

5. method according to claim 3, wherein said sintering process is carried out under higher than an atmospheric pressure, and sintering temperature is 550-950 DEG C.

6. method according to claim 5, wherein said pressure is 1-20GPa.

7. method according to claim 3, wherein said precursor comprises Li, Cd, Mn, P.

8. method according to claim 3, wherein said precursor comprises Li ₃p, Cd, Mn, P, CdP, MnP.

9. method according to claim 3, wherein said sintering process is carried out in rare gas element.

10. method according to claim 3, wherein said sintering process is carried out in vacuum environment.