Interdependence of magnetism and superconductivity in the borocarbide TmNi2B2C

TL;DR

This paper reports the discovery of a new antiferromagnetic phase in TmNi2B2C, revealing the complex interplay between magnetism and superconductivity, supported by neutron diffraction experiments and theoretical calculations.

Contribution

It introduces a new antiferromagnetic phase in TmNi2B2C and analyzes how superconductivity influences magnetic interactions and ordering.

Findings

Discovery of a new antiferromagnetic phase with Q_A = (0.48,0,0).

Magnetic phase appears above 0.9 T magnetic field.

Superconductivity suppresses ferromagnetic RKKY interactions and affects magnetic ordering.

Abstract

We have discovered a new antiferromagnetic phase in TmNi2B2C by neutron diffraction. The ordering vector is Q_A = (0.48,0,0) and the phase appears above a critical in-plane magnetic field of 0.9 T. The field was applied in order to test the assumption that the zero-field magnetic structure at Q_F = (0.094,0.094,0) would change into a c-axis ferromagnet if superconductivity were destroyed. We present theoretical calculations which show that two effects are important: A suppression of the ferromagnetic component of the RKKY exchange interaction in the superconducting phase, and a reduction of the superconducting condensation energy due to the periodic modulation of the moments at the wave vector Q_A.