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arXiv · 1712.02853

Orphan spins and bound in-gap states in the $S={5\over2}$ 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
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Abstract

CaFe$_{2}$O$_{4}$ is an anisotropic $S={5\over 2}$ antiferromagnet with two competing $A$ ($\uparrow \uparrow \downarrow \downarrow$) and $B$ ($\uparrow \downarrow \uparrow \downarrow$) 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$_{4}$.

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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. 2017-12-07. Orphan spins and bound in-gap states in the $S={5\over2}$ antiferromagnet CaFe$_{2}$O$_{4}$. https://doi.org/10.1103/physrevlett.119.257204

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