Singular field response and singular screening of vacancies in antiferromagnets

TL;DR

This paper reveals that vacancies in antiferromagnets exhibit a singular magnetic response due to a universal screening cloud, affecting their magnetic moments in weak magnetic fields, with implications for understanding magnetic screening phenomena.

Contribution

It uncovers the universal and singular nature of vacancy screening in antiferromagnets and its impact on magnetic response in weak fields.

Findings

Vacancy magnetic moments differ in zero and finite fields as h->0.

Universal screening cloud causes singular response.

Perfect screening occurs in spin-flop states at weak fields.

Abstract

For isolated vacancies in ordered local-moment antiferromagnets we show that the magnetic-field linear-response limit is generically singular: The magnetic moment associated with a vacancy in zero field is different from that in a finite field h in the limit h->0. The origin is a universal and singular screening cloud, which moreover leads to perfect screening as h->0 for magnets which display spin-flop bulk states in the weak-field limit.