Mahata, Partha ; Natarajan, Srinivasan ; Panissod, Pierre ; Drillon, Marc (2009) Quasi-2D XY magnetic properties and slow relaxation in a body centered metal organic network of [Co4] clusters Journal of the American Chemical Society, 131 (29). pp. 10140-10150. ISSN 0002-7863
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Official URL: http://pubs.acs.org/doi/abs/10.1021/ja9017539
Related URL: http://dx.doi.org/10.1021/ja9017539
Abstract
Octahedral Co2+ centers have been connected by μ3-OH and μ2-OH2 units forming [Co4] clusters which are linked by pyrazine forming a two-dimensional network. The two-dimensional layers are bridged by oxybisbenzoate (OBA) ligands giving rise to a three-dimensional structure. The [Co4] clusters bond with the pyrazine and the OBA results in a body-centered arrangement of the clusters, which has been observed for the first time. Magnetic studies reveal a noncollinear frustrated spin structure of the bitriangular cluster, resulting in a net magnetic moment of 1.4 μB per cluster. For T > 32 K, the correlation length of the cluster moments shows a stretched-exponential temperature dependence typical of a Berezinskii-Kosterlitz-Thouless model, which points to a quasi-2D XY behavior. At lower temperature and down to 14 K, the compound behaves as a soft ferromagnet and a slow relaxation is observed, with an energy barrier of ca. 500 K. Then, on further cooling, a hysteretic behavior takes place with a coercive field that reaches 5 T at 4 K. The slow relaxation is assigned to the creation/annihilation of vortex-antivortex pairs, which are the elementary excitations of a 2D XY spin system.
Item Type: | Article |
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Source: | Copyright of this article belongs to American Chemical Society. |
ID Code: | 27764 |
Deposited On: | 11 Dec 2010 07:57 |
Last Modified: | 04 Mar 2011 06:05 |
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