Min Ge

Critical phenomenon of the near room temperature skyrmion material FeGe.

The cubic B20 compound FeGe, which exhibits a near room temperature skyrmion phase, is of great importance not only for fundamental physics such as nonlinear magnetic ordering and solitons but also for future application of skyrmion states in spintronics. In this work, the critical behavior of the cubic FeGe is investigated by means of bulk dc-magnetization. We obtain the critical exponents (β = 0.336 ± 0.004, γ = 1.352 ± 0.003 and β = 5.276 ± 0.001), where the self-consistency and reliability are verified by the Widom scaling law and scaling equations. The magnetic exchange distance is found to decay as r−4.9, which is close to the theoretical prediction of 3D-Heisenberg model (r−5). The critical behavior of FeGe indicates a short-range magnetic interaction. Meanwhile, the critical exponents also imply an anisotropic magnetic coupling in this system.

Enhanced electrical conductivity and diluted Ir4+ spin orders in electron doped iridates Sr2–xGaxIrO4

Sr2IrO4 represents a fascinating system to study comparable electronic correlations and spin-orbit couplings, and recently attracts considerable attention in high-temperature superconductivity. Here, we report on the transport and magnetic properties in gallium-doped Sr2IrO4. A metallic state is discovered when doping x is over 0.1, which could be understood in terms of the quickly decreased energy gap and increased carrier concentration. In addition to the high-temperature magnetic transition (TC > 200 K), a low-temperature one ( TC′) is also observed for the x = 0.05–0.10 samples. Both of the magnetic states are found to be canted antiferromagnetism. The low-temperature phase is strongly depressed by doping and vanishes when doping is further increased, which is probably stabilized by the long-way exchange interactions of diluted Ir4+ spins via Ir3+ ions. Our studies provide an insight into the electrical and magnetic states tuned by chemical doping in Sr2IrO4, thereby facilitating the seeking of superc...

Anisotropic magnetic coupling with a two-dimensional characteristic in noncentrosymmetric Cr11Ge19.

In this work, we successfully synthesize the single crystal Cr11Ge19. The magnetism of the noncentrosymmetric Cr11Ge19 with itinerant ferromagnetic ground state is thoroughly investigated on the single crystal. Based on the variation measurements including the angular rotation, temperature, and magnetic field dependence of magnetization, we find that this material exhibits strong magnetic anisotropy along the c-axis. To clearly reveal the magnetic interactions, the critical behavior is studied using the modified Arrott plot, the Kouvel-Fisher method, and the critical isotherm technique. Combining these different methods, three main critical exponents (β, γ, and δ) are obtained. The critical exponent β is close to the theoretical prediction of a three-dimensional XY model with spin-dimensionality n = 2, indicating two-dimensional magnetic coupling. Meanwhile, the critical exponent γ suggests that the magnetic interaction is of long-range type with magnetic exchange distance decaying as J(r) ≈ r−4.61. We propose that the ferromagnetic ground state of Cr11Ge19 is formed by the polarized magnetic moments along the c-axis, while the long-range magnetic coupling is established within the ab plane.

Spin-dimensionality change induced by Co-doping in the chiral magnet Fe1−xCoxSi

Dimensionality is one of the most important parameters in the determination of the physical properties. Therefore, tuning of effective dimensionality is of significant importance for modulating the functionality of materials. In this work, we find that the spin-dimensionality can be changed by Co-doping in the Fe1−x Co x Si system. Investigation of the critical behavior shows that the effective critical exponents for x = 0.3 agree with the three-dimensional (3D) Heisenberg model with (d is the spatial-dimensionality, and n is the spin-dimensionality). With the increase of Co-content, the effective critical exponents for x = 0.5 fulfill the 3D-XY model with , while those for x = 0.6 approach the 3D-Ising model with . These results indicate the lowering of the spin-dimensionality with the increase of Co-content in Fe1−x Co x Si. We suggest that the modulation of the spin-dimensionality in Fe1−x Co x Si should result from the enhancement of the anisotropic magnetic interaction induced by the doping of Co.

Electron paramagnetic resonance study of the f–d interaction in pyrochlore iridate Gd2Ir2O7

The pyrochlore iridate has been investigated by means of the electron paramagnetic resonance spectroscopy. A magnetic transition at 20 K is found in addition to the transition at 130 K, which has not been reported previously. The phase transition at , which corresponds to a resistivity transition, is resulted from the long-range spin ordering of ions in all-in/all-out state. However, the magnetic transition at , which is regardless of resistivity transition, is not caused by but ions. Both of the magnetic transitions are irrelevant to the lattice distortion. We suggest that the competition between the enhanced paramagnetism of ions and the f–d interaction should be responsible for the magnetic transition at .

MICROMAGNETISM INDUCED BY THE UNPAIRED ELECTRONS IN InSb SINGLE CRYSTAL

In this paper, our experimental results demonstrate that the micromagnetism of InSb is determined by J (where J = L+S) instead of S of unpaired electrons due to the strong spin–orbit coupling. The results of macromagnetism show that the magnetism is diamagnetic, which comes from the Lamor moment of localized electrons and Landau diamagnetic moment of conduction electrons. Below 160 K, ferromagnetic ordering of J, which is induced by the interaction between J, also promotes the appearance of metallic behavior which is different from the well-known band theory.