Structural Modification and Metamagnetic Anomaly in the Ordered State of CeOs2Al10

TL;DR

This study investigates the structural, magnetic, and electronic properties of CeOs2Al10, revealing a phase transition with superlattice formation, anisotropic magnetic behavior, and a metamagnetic anomaly, contributing to understanding complex correlated electron systems.

Contribution

The paper reports the discovery of a structural modification and metamagnetic anomaly in CeOs2Al10, providing new insights into its ordered state and phase transition mechanisms.

Findings

Superlattice reflections indicate structural modification below 15 K.

Electrical resistivity suggests gap opening in the conduction band.

Metamagnetic anomaly occurs at 6-8 T when magnetic field is along the c axis.

Abstract

A caged compound CeOs2Al10, crystallizing in the orthorhombic YbFe2Al10-type structure, undergoes a mysterious phase transition at T_0=29 K. We report the results of electron diffraction, magnetization, and magnetoresistance for single crystals. Superlattice reflections characterized by a wave vector q = (0, -2/3, 2/3) observed at 15 K indicate a structural modification in the ordered state. Activation-type behavior of the electrical resistivity along the three principal axes below 50 K suggests gap opening in the conduction band. The magnetic susceptibility \chi = M/B is highly anisotropic, \chi_a>\chi_c>\chi_b, all of which sharply decrease on cooling below T_0. Furthermore, a metamagnetic anomaly in the magnetization and a step in the magnetoresistance occur at B=6-8 T only when the magnetic field is applied parallel to the orthorhombic c axis. However, T_0 hardly changes under magnetic fields up to 14 T, irrespective of the field direction. By using these data, we present a B-T phase diagram and discuss several scenarios for the mysterious transition.