As the first intrinsic magnetic topological insulator , MnBi 2 Te 4 has provided a material platform for the realization of various novel physical phenomena arising from the interaction between magnetism and band topology. Here, transition element Zn - doped MnBi 2 Te 4 crystals of millimeter size, synthesized by using self-flux method, are reported. With increasing Zn content, the hexagonal lattice shrinks, and the Raman frequencies show a red shift. All samples undergo a transition from A - type antiferromagnetic (A - AFM) to canted antiferromagnetic (CAFM) to ferromagnetic (FM) under magnetic field . The antiferromagnetic ordering temperature slightly increases from 24.2 K for MnBi 2 Te 4 to 25.2 K for Mn 0.75 Zn 0.25 Bi 2 Te 4 . The transition field from AFM to CAFM decreases from 3.4 T for x = 0–3.07 T for x = 0.25. Isothermal magnetization data suggest that the single - ion anisotropy of Mn 2+ decrease and the interlayer magnetic interaction increase slightly due to the diluted magnetic ions and unit cell shrinkage. Samples Mn 0.9 Zn 0.1 Bi 2 Te 4 and Mn 0.8 Zn 0.2 Bi 2 Te 4 show metallic conduction with a cusplike anomaly at around T N ≈ 24 K, corresponding to a long - range antiferromagnetic (AFM) transition. The increase of T N and decrease of transition field ( H c S F ) upon Zn doping, make it possible to manipulate magnetic and electrical properties in topological insulators by non - magnetic element substitution, which is of great significance for further application in quantum information storage and spintronics .
Haiyang Liu,Zongnan Zhang,Yingqiu Li,Yaping Wu,Zhiming Wu,Xu Li,Chunmiao Zhang,Feiya Xu,Junyong Kang
Achieving valley pseudospin with large polarization is crucial in the implementation of quantum information applications. Transition metal dichalcogenides (TMDC) with different phase structures provide an ideal platform for valley modulation. The valley splitting has been achieved in hybrid phase WSe2, while its valley polarization remains unstudied. Magnetic field controllable valley polarization is explored in WSe2 with coexistence of H and T phases by an all-optical route. A record high valley polarization of 58.3% is acquired with a 19.9% T phase concentration under a 4-T magnetic field and nonresonant excitation. The enhanced valley polarization is dependent on the phase component and shows various increasing slopes, owing to the synergy between the T phase WSe2 and the magnetic field. The magnetic field controlled local magnetic momentums are revealed as the mechanism for the large valley polarization in H / T-WSe2. This speculation is also verified by theoretical simulations of the nonequilibrium spin density. These results display a considerable valley magnetic response in phase-engineered TMDC and provide a large-scale scheme for valley polarization applications.
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