Orphan Spins in the S=5/2 Antiferromagnet CaFe_{2}O_{4}

C Stock; E E Rodriguez; N Lee; F Demmel; P Fouquet; M Laver; Ch Niedermayer; Y Su; K Nemkovski; M A Green; J A Rodriguez-Rivera; J W Kim; L Zhang; S-W Cheong

doi:10.1103/PhysRevLett.119.257204

Orphan Spins in the S=5/2 Antiferromagnet CaFe_{2}O_{4}

Phys Rev Lett. 2017 Dec 22;119(25):257204. doi: 10.1103/PhysRevLett.119.257204. Epub 2017 Dec 22.

Authors

C Stock¹, E E Rodriguez², N Lee³, F Demmel⁴, P Fouquet⁵, M Laver⁶, Ch Niedermayer⁷, Y Su⁸, K Nemkovski⁸, M A Green⁹, J A Rodriguez-Rivera^{10

11}, J W Kim³, L Zhang¹², S-W Cheong³

Affiliations

¹ School of Physics and Astronomy and Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom.
² Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA.
³ Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA.
⁴ ISIS Facility, Rutherford Appleton Labs, Chilton, Didcot OX11 0QX, United Kingdom.
⁵ Institute Laue-Langevin, 6 rue Jules Horowitz, Boite Postale 156, 38042 Grenoble Cedex 9, France.
⁶ School of Metallurgy and Materials, University of Birmingham, B15 2TT, United Kingdom.
⁷ Laboratory for Neutron Scattering, Paul Scherrer Institut, CH-5232 Villigen, Switzerland.
⁸ Jülich Centre for Neuton Science JCNS, Forschungszentrum Jülich GmbH, Outstation at MLZ, Lichtenbergstraße 1, D-85747 Garching, Germany.
⁹ School of Physical Sciences, University of Kent, Canterbury CT2 7NH, United Kingdom.
¹⁰ NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA.
¹¹ Department of Materials Science, University of Maryland, College Park, Maryland 20742, USA.
¹² Laboratory for Pohang Emergent Materials and Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology, Pohang 790-784, Korea.

PMID: 29303328
DOI: 10.1103/PhysRevLett.119.257204

Abstract

CaFe_{2}O_{4} is an anisotropic S=5/2 antiferromagnet with two competing A (↑↑↓↓) and B (↑↓↑↓) magnetic order parameters separated by static antiphase boundaries at low temperatures. Neutron diffraction and bulk susceptibility measurements, show that the spins near these boundaries are weakly correlated and a carry an uncompensated ferromagnetic moment that can be tuned with a magnetic field. Spectroscopic measurements find these spins are bound with excitation energies less than the bulk magnetic spin waves and resemble the spectra from isolated spin clusters. Localized bound orphaned spins separate the two competing magnetic order parameters in CaFe_{2}O_{4}.