Magnetic Phase Diagram and Field Induced Magnetic Structure in DyCo₂Si₂

抄録

The H-T magnetic phase diagram and field induced magnetic structure in tetragonal DyCo₂Si₂ with a two-step metamagnetic process have been determined by magnetization and neutron diffraction experiments using a single crystal as well as specific heat experiment on a polycrystalline sample. Three magnetic phases exist below T_N=23, K. A simple antiferromagnetic structure (phase I), with the propagation vector Q₁=(0, , 0, , 1) and moments along the c-axis, is stable below 21, K under low field. The intermediate field induced magnetic structure (phase II) is characterized by two additional propagation vectors: i) Q₀=(0, , 0, , 0) and ii) Q₂=(1/2, , 1/2, , 1/2) which is a sub-harmonics of (1, , 1, , 1) (≡ Q₁) and consists of ferromagnetic (111) planes with the sequence of + + + -. It has a resultant magnetization of half the saturation value, i.e. 5.0, μ _B/f.u., at low temperature. Between T_N and 21, K, an antiferromagnetic phase (phase III) with an unknown structure appears.