Anomalous magnetic properties near the spin-flop bicritical point in Mn(2)AS(4) (A = Si and Ge).
The magnetic properties of the single crystalline Mn(2)AS(4) (A = Si and Ge) with an olivine structure, which are the uniaxially anisotropic antiferromagnets (the b axis as an easy axis), were investigated. Near the Néel temperature, both compounds exhibit the contrastive magnetic responses along the c axis, namely, the spontaneous weak ferromagnetism in A = Si and the significant enhancement of the differential susceptibility (dM/dH) under the small magnetic field in A = Ge. When A = Ge, we also observed the evolution of dM/dH along the axis at low temperatures. We discuss these phenomena on the basis of the magnetic field-temperature (H-T) phase diagram with the spin-flop bicritical point (H(BP), T(BP). The role of the thermal or quantum fluctuation was stressed.
Ohgushi
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Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
Ueda
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Y