Antiferromagnetic order in CeCoIn5 oriented by spin-orbital coupling

TL;DR

This paper explains how spin-orbit coupling fixes the direction of antiferromagnetic modulations in CeCoIn5, supported by phenomenological arguments and microscopic derivations of susceptibility dependence.

Contribution

It provides a novel explanation for the magnetic field orientation effects in CeCoIn5 based on spin-orbit coupling, combining phenomenological and microscopic approaches.

Findings

Spin-orbit coupling explains the fixed direction of antiferromagnetic modulations.

Microscopic derivation shows susceptibility dependence on magnetic field orientation.

Supports experimental observations of magnetic order in CeCoIn5.

Abstract

An incommensurate spin density wave ($Q$ phase) confined inside the superconducting state at high basal plane magnetic field is an unique property of the heavy fermion metal CeCoIn$_5$. The neutron scattering experiments and the theoretical studies point out that this state come out from the soft mode condensation of magnetic resonance excitations. We show that the fixation of direction of antiferromagnetic modulations by a magnetic field reported by Gerber et al., Nat. Phys. {\bf 10}, 126 (2014) is explained by spin-orbit coupling. This result, obtained on the basis of quite general phenomenological arguments, is supported by the microscopic derivation of the $\chi_{zz}$ susceptibility dependence on the mutual orientation of the basal plane magnetic field and the direction of modulation of spin polarization in a multi-band metal.