arXiv subjects

M. F. Collins

Publications and source records attributed to M. F. Collins.

2 recordsLinked to original sources

arXiv1997

Triangular Antiferromagnets

In this article we review the effects of magnetic frustation in the stacked triangular lattice. Frustration increases the degeneracy of the ground state, giving rise to different physics. In particular it leads to unique phase diagrams with multicritical points and novel critical phenomena. We describe the confrontation of theory and experiment for a number of systems with differing magnetic Hamiltonians; Heisenberg, Heisenberg with easy-axis anisotropy, Heisenberg with easy-plane anisotropy, Ising and singlet ground state. Interestingly each leads to different magnetic properties and phase diagrams. We also describe the effects of ferromagnetic, rather than antiferromagnetic, stacking and of small distortions of the triangular lattice.

cond-mat↗

arXiv1997

Less than 50% sublattice polarization in an insulating S=3/2 kagome' antiferromagnet at low T

We have found weak long range antiferromagnetic order in the quasi-two-dimensional insulating oxide $ KCr_3(OD)_6(SO_4)_2$ which contains Cr$^{3+}$ S=3/2 ions on a kagomé lattice. In a sample with $\approx$ 76% occupancy of the chromium sites the ordered moment is 1.1(3)$μ_B$ per chromium ion which is only one third of the Néel value $gμ_BS=3μ_B$. The magnetic unit cell equals the chemical unit cell, a situation which is favored by inter-plane interactions. Gapless quantum spin-fluctuations ($Δ/k_B <0.25$K) with a bandwidth of 60K >> $T_N$ = 1.6K are the dominant contribution to the spin correlation function, $S(Q,ω)$ in the ordered phase.

cond-mat.str-el↗