The Two-Dimensional Square-Lattice S=1/2 Antiferromagnet Cu(pz)$_2$(ClO$_4$)$_2
Phys. Rev. B 81, 134409 (2010) We present an experimental study of the two-dimensional S=1/2 square-lattice antiferromagnet Cu(pz)$_2$(ClO$_4$)$_2$ (pz denotes pyrazine - $C_4H_4N_2$) using specific heat measurements, neutron diffraction and cold-neutron spectroscopy. The magnetic field dependence o...
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Main Authors | , , , , , , , , |
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Format | Journal Article |
Language | English |
Published |
14.07.2010
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Subjects | |
Online Access | Get full text |
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Summary: | Phys. Rev. B 81, 134409 (2010) We present an experimental study of the two-dimensional S=1/2 square-lattice
antiferromagnet Cu(pz)$_2$(ClO$_4$)$_2$ (pz denotes pyrazine - $C_4H_4N_2$)
using specific heat measurements, neutron diffraction and cold-neutron
spectroscopy. The magnetic field dependence of the magnetic ordering
temperature was determined from specific heat measurements for fields
perpendicular and parallel to the square-lattice planes, showing identical
field-temperature phase diagrams. This suggest that spin anisotropies in
Cu(pz)$_2$(ClO$_4$)$_2$ are small. The ordered antiferromagnetic structure is a
collinear arrangement with the magnetic moments along either the
crystallographic b- or c-axis. The estimated ordered magnetic moment at zero
field is m_0=0.47(5)mu_B and thus much smaller than the available single-ion
magnetic moment. This is evidence for strong quantum fluctuations in the
ordered magnetic phase of Cu(pz)$_2$(ClO$_4$)$_2$. Magnetic fields applied
perpendicular to the square-lattice planes lead to an increase of the
antiferromagnetically ordered moment to m_0=0.93(5)mu_B at mu_0H=13.5T -
evidence that magnetic fields quench quantum fluctuations. Neutron spectroscopy
reveals the presence of a gapped spin excitations at the antiferromagnetic zone
center, and it can be explained with a slightly anisotropic nearest neighbor
exchange coupling described by J_1^{xy}=1.563(13)meV and
J_1^z=0.9979(2)J_1^{xy}. |
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DOI: | 10.48550/arxiv.1007.2279 |