J.W. Huang

Landau level splitting in Cd3As2 under high magnetic fields.

Three-dimensional topological Dirac semimetals (TDSs) are a new kind of Dirac materials that exhibit linear energy dispersion in the bulk and can be viewed as three-dimensional graphene. It has been proposed that TDSs can be driven to other exotic phases like Weyl semimetals, topological insulators and topological superconductors by breaking certain symmetries. Here we report the first transport experiment on Landau level splitting in TDS Cd3As2 single crystals under high magnetic fields, suggesting the removal of spin degeneracy by breaking time reversal symmetry. The detected Berry phase develops an evident angular dependence and possesses a crossover from non-trivial to trivial state under high magnetic fields, a strong hint for a fierce competition between the orbit-coupled field strength and the field-generated mass term. Our results unveil the important role of symmetry breaking in TDSs and further demonstrate a feasible path to generate a Weyl semimetal phase by breaking time reversal symmetry.

Spin reorientation and spin-flop transition in multiferroic manganites Y1–xTbxMnO3 (x = 0, 0.1, 0.2) single crystals

We investigated the structure and magnetic properties of the multiferroic hexagonal manganite Y1−xTbxMnO3 (x = 0, 0.1, 0.2) single crystals. At 23 K, a Mn spin reorientation transition, which is not reported in the parent compound YMnO3, is observed in Y0.8Tb0.2MnO3. At a lower temperature, another new transition is observed in the doping system, which is attributed to the formation of long range antiferromagntic order of the doped Tb3+ moments. Based on the experimental results, we suggest that the effect of Tb doping is to bring about the increase of the Mn-O-Mn bond angle and the relief of the magnetic frustration. With increasing the doping level, for x = 0.2, when a magnetic field is applied parallel to the c axis, the field induced spin-flop transition is appeared, which indicates the reorientation of the Mn3+ moments along with the field-induced ferromagnetic ordering of the Tb3+ moments. These results suggest that the possibility of the Tb doping can change the magnetic structure and ferroelectric...

Magnetic field-induced metamagnetic transitions of Pr0.5Ca0.5Mn0.97Ga0.03O3

Measurements of isothermal magnetization and electrical transport on Pr0.5Ca0.5Mn0.97Ga0.03O3 have been performed in a magnetic field up to 15 T. Two distinct metamagnetic transitions, which may relate to the collapse of the pseudo-CE-type and CE-type antiferromagnetic phases (CE, a composite antiferromagnetic structure composed of a chequeboard of alternating C and E type), have been observed in the temperature region of 2.5–140 K. Different from the traditional magnetization steps, the two metamagnetic transitions are not dependent on the field sweep rate. These peculiar features are sensitive to the microstructure of the sample. A temperature-field phase diagram has been constructed and found to exhibit a minimum critical field, similar to other phase-separated systems.

The enhanced spontaneous dielectric polarization in Ga doped CuFeO2

The magnetic and dielectric polarization properties of the single crystal samples of CuFe1−xGaxO2 (x = 0 and 0.02) are investigated. Experimental results show that the magnetization and dielectric polarizations are anisotropy and coupled together. Compared with pure CuFeO2, in the case with the magnetic field parallel to the c axis, a field-induced phase transition with a hysteresis is clearly observed between the five-sublattice (5SL) and three-sublattice (3SL) phases. Specially, an obvious spontaneous dielectric polarization is observed in CuFe0.98Ga0.02O2 in a lower magnetic field region, indicating that the Ga doping has an effect on the enhancement of spontaneous dielectric polarization. Based on the dilution effect, change of exchange interaction, and partial release of the spin frustration due to the structural modulation of the Ga ion dopant, the origin of the magnetization, and spontaneous polarization characteristics are discussed and the complete dielectric polarization diagrams are assumed.

Avalanche transition with super-bandwidth magnetic field response in (La0.73Bi0.27)0.67Ca0.33MnO3

The magnetic and electrical behaviors of an optimizing doping (La0.73Bi0.27)0.67Ca0.33MnO3 were investigated. An avalanche transition with a super-bandwidth of magnetic field response, in which the magnetic field sweep rate ranging from 10 Oe/s to 4886.8 T/s, was observed in the manganite. The insensitivity of the critical field of the avalanche transition to the magnetic field weep rates could not be described well within the framework of martensitic transition scenario. Based on the hybridization between the Bi3+-6s lone pair electrons and O2–2p electrons, we assume that the observed super-bandwidth avalanche transition is an intrinsic behavior resulting from the s-p hybridization. The robust transition makes the material extremely attractive for potential applications in super-bandwidth magnetic field response sensor. The simple structure of the current system also provides an ideal platform for understanding the physics underlying the avalanche transition.

High magnetic field induced spin flip/flop behavior and magnetic phase diagram of CuFe{sub 1−x}Ga{sub x}O{sub 2}

Abstract The structure and magnetic properties of non-magnetic Ga 3+ ion doped CuFe 1− x Ga x O 2 ( x =0, 0.03, and 0.05) single crystal samples were investigated. X-ray diffraction patterns analysis confirms that the samples are single-phase crystallizing. Doping effect on the magnetic behavior of the ground state and the field-induced spin flip/flop transitions were detected. The transition temperatures and critical magnetic fields of the spin flip/flop, as well as the magnetic hysteresis directly depend on the Ga 3+ doping level. Such doping effects may associate with the competition between dilution effect (partial release of spin frustration) and the induced local magnetic moment, which is the result of the changed magnetic coupling both inter- and intra-planes of Fe ions. Based on the experimental results, the effects of Ga 3+ doping on the spin flip/flop behavior and a detailed high field magnetic diagram were assumed.