Impurity-induced magnetic order in the mixture of two spin gap systems (CH3)2CHNH3CuCl3 and (CH3)2CHNH3CuBr3

The ground state of the solid solution of the two spin gap systems (CH3)2CHNH3CuCl3 and (CH3)2CHNH3CuBr3 has been investigated by 1H-NMR. The existence of a magnetic ordering in the sample with the Cl-content x=0.85 was clearly demonstrated by a drastic splitting in a resonance line at low temperatures below TN=13.5K. The observed NMR spectra in the ordered state was qualitatively consistent with the simple antiferromagnetic state.Comment: QuBS200

Magnetic transition in the Heusler compounds Fe3-xMnxSi

It has been shown that Fe2MnSi exhibits a ferromagnetic transition at Tc and an antiferromagnetic transition at a lower temperature, TA, to a phase referred to as the AF phase. In a recent study on Fe1.3Mn1.7Si, another antiferromagnetic transition at a temperature lower than TA, defined as TA2, was found, with the phase below TA2 referred to as the AF2 phase. In this study, magnetic properties of Fe3-xMnxSi are investigated for an x range of 1.65 ≤ x ≤ 1.85 in order to study theses transitions with varying x. For x ≥ 1.75, a transition characterized by a rather rapid decrease in the temperature dependence of magnetization is observed at a temperature lower than TA at fields higher than ∼2 T. This implies the AF2-AF transition exists for x ≥ 1.75 as for x = 1.7. The magnetic field where the AF2-AF transition occurs increases with x, whereas at lower fields TA2 does not depend strongly on x. Meanwhile, at near zero field, the ferromagnetic transition and spontaneous magnetization disappears for x ≥ 1.75, in contrast to the case for x = 1.7. This implies that the transition from paramagnetism directly to the AF2 phase occurs at low fields. These results are summarized in the B-T magnetic phase diagram

Thermodynamic properties of Heusler Fe2VSi

We investigated temperature, T, dependence of magnetization, M(T), electrical resistivity, ρ(T), and specific heat, Cp(T), for the Heusler compound Fe2VSi. M(T) shows anomalies at TN1 ∼ 115 K and at TN2 ∼ 35 K. The anomaly at TN1 is caused by the magnetic transition with a crystal structural change. On the other hand, ρ(T) and Cp(T) show only anomaly at TN1, and no trace of anomaly at TN2 is observed. Because of the irreversibility of M(T), which is the characteristic of spin-glass freezing, appears below TN2, a spin-glass freezing may occur at TN2. From the analogy of the Heusler compound (Fe1−xVx)3Si with the cubic D03 crystal structure, (0 ≤ x ≤ 0.2), we suggested that the atomic disorder of V site by the Fe atoms gives rise to the magnetic frustration. This could be cause for the spin-glass freezing. By the Clausius-Clapeyron relation, pressure, P, derivative of TN1, (dTN1dP), is estimated to be ∼−10 K/Gpa