K. Kindo

Metamagnetism of η-carbide-type transition-metal carbides and nitrides

η-carbide-type transition-metal compounds include the frustrated stella quadran-gula lattice. Due to characteristics of the lattice, we expect subtle transitions between frustrated and non-frustrated states. Here, we report metamagnetic transitions newly found in η-carbide-type compounds Fe3W3C, Fe6W6C and Co6W6C.

Single crystal growth and magnetic property of NH4CuPO4 · H2O

We synthesized single crystals of NH4CuPO4 H2O by a chemical reaction in aqueous solutions. Magnetization and specific heat are well reproduced by a dimer model, and NH4CuPO4 H2O does not show any field-induced magnetic phase transitions. The interdimer interactions would be too weak to observe field-induced phase transitions.

Magnetic properties of exchange-enhanced Pauli paramagnetic metals AeCo2P2 (Ae = Sr, Ba)

We have synthesized single crystals of AeCo2P2 (Ae = Sr, Ba) and polycrystalline powder sample of Sr1−x Ba x Co2P2, and measured their magnetic properties. SrCo2P2 shows an itinerant-electron metamagnetic transition at Hc = 600 kOe and its temperature dependent magnetic susceptibility shows characteristic two anomalies at T max1 = 25 and T max2 = 115 K, suggesting it is in the vicinity of a ferromagnetic quantum critical point. While, BaCo2P2 does not show the metamagnetic transition with the applied field up to 600 kOe, and its magnetic susceptibility shows only one anomaly corresponding to T max1 at 33 K. In addition, the Weiss temperature of Sr1−x Ba x Co2P2, decreases to negative as x increases. These results indicate the system recede from the quantum critical point by the Ba substitution.

Spin-singlet state in Sb2VO5

We have measured the high-field magnetization of a quasi-one dimensional S=1/2 chain compound Sb2VO5, which was proposed as a new candidate of the inorganic spin-Peierls (SP) system. The magnetization measured at 4.2 K exhibits a clear inflection at around 23 T, indicating obviously the excitation from a spin singlet ground state to a triplet state. Absence of anomalies in specific heat and X-ray diffraction points to no SP transition, and the analysis of the susceptibility suggests that this compound is an alternating spin chain system.