Zero-field random-field effect in diluted triangular lattice antiferromagnetCuFe1−xAlxO2

Abstract

We performed neutron scattering experiments on a diluted triangular lattice antiferromagnet (TLA),CuFe1−xAlxO2 with x = 0.10. The detailed analysis of the scattering profiles revealed that the scattering function ofmagnetic reflection is described as the sum of a Lorentzian term and a Lorentzian-squaredterm with anisotropic width. The Lorentzian-squared term dominating at low temperature isindicative of the domain state in the prototypical random-field Ising model. Taking account ofthe sinusoidally amplitude-modulated magnetic structure with incommensurate wavenumber inCuFe1−xAlxO2 with x = 0.10, we conclude that the effective random field arises even at zero field, owing tothe combination of site-random magnetic vacancies and the sinusoidal structurethat is regarded as a partially disordered (PD) structure in a wide sense, asreported in the typical three-sublattice PD phase of a diluted Ising TLA,CsCo0.83Mg0.17Br3 (vanDuijn et al 2004 Phys. Rev. Lett. 92 077202). While the previous study revealed the existence of a domainstate in CsCo0.83Mg0.17Br3 by detecting magnetic reflections specific to the spin configuration near thedomain walls, our present study revealed the existence of a domain state inCuFe1−xAlxO2 (x = 0.10) by determination of the functional form of the scattering function.