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Durham University

Department of Physics

Staff profile

Publication details for Professor Tom Lancaster

Blackmore, W J A, Brambleby, J, Lancaster, T, Clark, S J, Johnson, R D, Singleton, J, Ozarowski, A, Schlueter, J A, Chen, Y-S, Arif, A M, Lapidus, S, Xiao, F, Williams, R C, Blundell, S J, Pearce, M J, Lees, M R, Manuel, P, Villa, D Y, Villa, J A, Manson, J L & Goddard, P A (2019). Determining the anisotropy and exchange parameters of polycrystalline spin-1 magnets. New Journal of Physics 21(9): 093025.

Author(s) from Durham

Abstract

Although low-dimensional S = 1 antiferromagnets remain of great interest, difficulty in obtaining highquality single crystals of the newest materials hinders experimental research in this area. Polycrystalline
samples are more readily produced, but there are inherent problems in extracting the magnetic properties
of anisotropic systemsfrom powder data. Following a discussion of the effect of powder-averaging on
various measurement techniques, we present a methodology to overcome this issue using thermodynamic
measurements. In particular wefocus on whether it is possible to characterise the magnetic properties of
polycrystalline, anisotropic samples using readily available laboratory equipment.We test the efficacy of
our method using the magnets[Ni(H2O)2(3,5-lutidine)4](BF4)2 and Ni(H2O)2(acetate)2(4-picoline)2,
which have negligible exchange interactions, as well as the antiferromagnet[Ni(H2O)2(pyrazine)2](BF4)2,
and show that we are able to extract the anisotropy parameters in each case. The results obtainedfrom the
thermodynamic measurements are checked against electron-spin resonance and neutron diffraction.We
also present a densityfunctional method, which incorporates spin–orbit coupling to estimate the size of the
anisotropy in [Ni(H2O)2(pyrazine)2](BF4)2.