C. Shang

Al3+ doping effects and high-field phase diagram of La0.5Sr0.5Mn1−x Al x O3

Magnetization measurements of La0.5Sr0.5Mn1−x Al x O3 (0 ≤ x ≤ 0.25) under pulsed high magnetic fields up to 50 T have been carried out, in which the Al3+ ions doping and magnetic field effects on the charge-ordering/antiferromagnetic to ferromagnetic phase transitions have been discussed. A triple-phase diagram with the critical field, doping level and temperature has been determined, in which the antiferromagntic and ferromagnetic phase boundaries were clearly defined. The change from long-range charge-ordered/antiferromagnetic phases to the robust short-range ones upon the Al3+-doping was observed. According to the experimental results, we assume that Al3+ ion doping at the Mn sites dilutes the Mn3+-O-Mn4+ network, weakens the double-exchange interaction and further suppresses the FM phase (metallic conduction), which leads to the critical magnetic fields destroying the antiferromagnetic order increase with the increase of the doping level.

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.

3D spin-flop transition in enhanced 2D layered structure single crystalline TlCo2Se2

The enhanced 2D layered structure single crystalline TlCo2Se2 has been successfully fabricated, which exhibits field-induced 3D spin-flop phase transitions. In the case of the magnetic field parallel to the c-axis (B//c), the applied magnetic field induces the evolution of the noncollinear helical magnetic coupling into a ferromagnetic (FM) state with all the magnetization of the Co ion parallel to the c-axis. A striking variation of the field-induced strain within the ab-plane is noticed in the magnetic field region of 20-30 T. In the case of the magnetic field perpendicular to the c-axis (B  ⊥  c), the inter-layer helical antiferromagnetic (AFM) coupling may transform to an initial canted AFM coupling, and then part of it transforms to an intermediate metamagnetic phase with the alignment of two-up-one-down Co magnetic moments and finally to an ultimate FM coupling in higher magnetic fields. The robust noncollinear AFM magnetic coupling is completely destroyed above 30 T. In combination with the measurements of magnetization, magnetoresistance and field-induced strain, a complete magnetic phase diagram of the TlCo2Se2 single crystal has been depicted, demonstrating complex magnetic structures even though the crystal geometry itself gives no indication of the magnetic frustration.