Nuclear spin-lattice relaxation time in UCoGe

TL;DR

This paper investigates the anisotropic magnetic properties and spin-lattice relaxation rates in the ferromagnetic superconductor UCoGe using NMR measurements and theoretical calculations, revealing field-dependent relaxation behaviors.

Contribution

It provides a detailed analysis of the anisotropic spin-lattice relaxation rates and their dependence on temperature and magnetic field orientations in UCoGe.

Findings

Maximum 1/T_1T near Curie temperature in perpendicular field

Field dependence of relaxation rate in b-direction

Field independence of relaxation rate along a-axis

Abstract

The NMR measurements performed on a single orthorhombic crystal of superconducting ferromagnet UCoGe (Y.Ihara et al, Phys. Rev. Lett. v.105, 206403 (2010)) demonstrate strongly anisotropic magnetic properties of this material. The presented calculations allow to establish the dependence of longitudinal spin-lattice relaxation rate from temperature and magnetic field. The value 1/T_1T in field perpendicular to spontaneous magnetisation directed along c-axis has maximum in vicinity of Curie temperature whereas it does not reveal similar behaviour in field parallel to the direction of spontaneous magnetisation. Also there was shown that the longitudinal spin-lattice relaxation rate is strongly field dependent when the field directed in b-crystallographic direction but field independent if magnetic field is oriented along a-axis.