Journal
PHYSICAL REVIEW B
Volume 74, Issue 2, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.74.024413
Keywords
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We have investigated the structural, magnetic, thermodynamic, and dielectric properties of polycrystalline CoCr2O4, an insulating spinel exhibiting both ferrimagnetic and spiral magnetic structures. Below T-c=94 K the sample develops long-range ferrimagnetic order, and we attribute a sharp phase transition at T-S approximate to 27 K to the onset of long-range spiral magnetic order. Neutron measurements confirm that the structure remains cubic at 80 K and at 11 K; the magnetic ordering by 11 K is seen to be rather complex. Density functional theory supports the view of a ferrimagnetic semiconductor with magnetic interactions consistent with noncollinear ordering. Capacitance measurements on CoCr2O4 show a sharp decrease in the dielectric constant at T-S, but also an anomaly showing thermal hysteresis falling between approximately T=50 and 57 K. We tentatively attribute the appearance of this higher-temperature dielectric anomaly to the development of short-range spiral magnetic order, and discuss these results in the context of utilizing dielectric spectroscopy to investigate noncollinear short-range magnetic structures. (c) 2006 American Institute of Physics.
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