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摘要: 利用高温固相反应法, 成功合成了一种新型块状稀磁半导体(La1–xSrx)(Zn1–xMnx)SbO(x = 0.025, 0.05, 0.075, 0.1). 通过(La3+, Sr2+)、(Zn2+, Mn2+)替换, 在半导体材料LaZnSbO中分别引入了载流子与局域磁矩. 在各掺杂浓度的样品中均可观察到铁磁有序相转变, 当掺杂浓度x = 0.1时, 其居里温度Tc达到了27.1 K, 2 K下测量获得的等温磁化曲线表明其矫顽力为5000 Oe. (La1–xSrx)(Zn1–xMnx)SbO与“1111”型铁基超导体母体LaFeAsO、“1111”型反铁磁体LaMnAsO具有相同的晶体结构, 且晶格参数差异很小, 为制备多功能异质结器件提供了可能的材料选择.Abstract: Diluted magnetic semiconductor (DMS) that combines the properties of spin and charge degrees of freedom, which has potential applications in the field of spintronic devices. In the 1990s, due to the breakthrough of low-temperature molecular beam epitaxy technology, scientists successfully synthesized III-V DMS (Ga, Mn)As, and developed some spintronics devices accordingly. However, the maximum Curie temperature of (Ga, Mn)As is only 200 K, which is still below room temperature that is required for practical applications. Searching for diluted magnetic semiconductors with higher Curie temperature and the exploring of their magnetism is still one of the focuses at present. In recent years, developed from iron-based superconductors, a series of novel magnetic semiconductors have been reported. These new DMSs have the advantages of decoupled charge and spin doping, and each concentration can be precisely controlled. In this paper, novel bulk diluted magnetic semiconductors (La1–xSrx)(Zn1–xMnx)SbO (x = 0.025, 0.050,0.075, 0.10) are successfully synthesized, with the highest Tc ~ 27.1 K for the doping level of x = 0.10. We dope Sr2+ and Mn2+ into the parent semiconductor material LaZnSbO to introduce holes and moments, respectively. The ferromagnetic ordered phase transition can be observed in the samples with various doping concentrations. A relatively large coercive field is observed to be ~ 5000 Oe from the iso-thermal magnetization measurement at 2 K. The (La1–xSrx)(Zn1–xMnx)SbO has the same crystal structure as the “1111-type” iron-based superconductor LaFeAsO, and the lattice parameter difference is very small. It provides a possible material choice for preparing the multifunctional heterojunction devices.
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Key words:
- diluted magnetic semiconductor /
- Curie temperature /
- magnetic ordering /
- coercivity
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图 1 (a) (La1–xSrx)(Zn1–xMnx)SbO的X射线衍射图, 杂质ZnSb由(*)标注; (b) LaZnSbO的晶体结构; (c) (La0.95Sr0.05)(Zn0.95Mn0.05)SbO的Rietveld精修结果; (d) (La1–xSrx)(Zn1–xMnx)SbO的晶格常数
Figure 1. (a) The X-ray diffraction patterns for (La1–xSrx)(Zn1–xMnx)SbO (x = 0.025, 0.05, 0.075, 0.1); Trace of impurities ZnSb (*) are marked; (b) the crystal structure of LaZnSbO; (c) the Rietveld refinement of (La0.95Sr0.05)(Zn0.95Mn0.05)SbO; (d) the lattice parameters of (La1–xSrx)(Zn1–xMnx)SbO.
图 2 (a) (La1–xSrx)(Zn1–xMnx)SbO分别在100 Oe的场冷和零场冷测量条件下的直流磁化强度; (b) (La1–xSrx)(Zn1–xMnx)SbO拟合后的
$ 1/({\rm{\chi }}-{\chi }_{0}) $ 结果, 箭头标注为外斯温度θ; (c) (La1–xSrx)(Zn1–xMnx)SbO磁化强度与温度之间的一阶导数关系(dM/dT), 箭头标注为样品的居里温度TC; (d)温度为2 K下的等温磁化强度曲线Figure 2. (a) The temperature dependence of DC magnetization for (La1–xSrx)(Zn1–xMnx)SbO measured under field-cooling (FC) and zero-field-cooling(ZFC) with external field of 100 Oe; (b) the plot of
$ 1/({\rm{\chi }}-{\chi }_{0}) $ versus T for (La1–xSrx)(Zn1–xMnx)SbO, and the arrow marked the Weiss Temperature$ \theta $ ; (c)the derivative of moment versus temperature for (La1–xSrx)(Zn1–xMnx)SbO, and the arrow marked the Curie Temperature; (d)iso-thermal magnetization for (La1–xSrx)(Zn1–xMnx)SbO at 2 K.表 1 “1111”型稀磁半导体、超导体、反铁磁体的相变温度
Table 1. The phase transition temperature of 1111-type dilute magnetic semiconductors, superconductors and antiferromagnets.
类型 结构 化学式 相变温度/K 稀磁半导体 (P4/nmm) (La, Ca)(Zn, Mn)AsO[7] 30(居里温度) (La, Sr)(Zn, Mn)AsO[8] 30 (La, Ba)(Zn, Mn)AsO[9] 40 (La, Ca)(Zn, Mn)SbO[10] 40 La(Zn, Mn, Cu)AsO[11] 8 La(Zn, Mn, Cu)SbO[12] 15 (La, Sr)(Cu, Mn)SO[13] 200 (Ba, K)F(Zn, Mn)As[14] 30 SrF(Zn, Mn, Cu)Sb[15] 40 超导体 (P4/nmm) LaFeAs(O, F)[16] 26 (超导转变温度) 反铁磁体 (P4/nmm) LaMnAsO[17] 317 (奈尔温度) LaMnSbO[18] 255 K 表 2 居里温度Tc、外斯温度θ、有效磁矩Meff、矫顽力Hc
Table 2. The Curie temperature Tc, the Weiss temperature θ, the effective moment Meff and the coercive field Hc.
掺杂浓度x Tc / K θ / K Meff / ( $ {\mu }_{\rm{B}}/{\rm{Mn}} $) Hc / Oe 0.025 10.0 10.5 4.32 16000 0.050 14.1 20.2 4.68 17000 0.075 23.2 33.0 4.84 3500 0.10 27.1 37.3 4.26 5000 -
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