Single Crystal Neutron Diffraction Study of the Magnetic Phase Diagram of the Heavy Fermion Superconductor UPd_2Al_3

概要

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The magnetic phase diagram of the heavy fermion superconductor UPd_2Al_3 (T_N=14.3 K)has been determined in magnetic fields up to 5 Tesla by single crystal neutron diffraction experiments, which were performed at several temperatures above and below the superconducting transition at T_c=1.8 K. Observed magnetic intensities correspond to the magnetic structure with a field-independent magnetic propagation vector k=[0, 0, 1/2]. A magnetic field applied in the hexagonal a-b plane gives rise to domain reorientations, in addition rotates the direction of the ordered magnetic moments against a small anisotropy in the easy a-b plane, and makes the moment directions perpendicular to the field direction. This model allows a quantitative analysis of the observed field dependence of magnetic peak intensities. No superconductivity-induced changes of the antiferromagnetic order in UPd_2Al_3 are observed in our experiments. However, an anomaly detected in the temperature dependence of the zero-field sublattice magnetization for 11 K≤T≤14.3 K indicates a change in the magnetic structure of UPd_2Al_3.
社団法人日本物理学会の論文
1994-02-15