Soft phonon behavior and magnetism at the low temperature structural phase transition of La1.65Nd0.35CuO4 |
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Authors: | B Keimer R J Birgeneau A Cassanho Y Endoh M Greven M A Kastner G Shirane |
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Institution: | (1) Center for Materials Science and Engineering, Massachusetts Institute of Technology, 02139 Cambridge, MA, USA;(2) Department of Physics, Tohoku University, Sendai 980, Japan;(3) Brookhaven National Laboratory, 11973 Upton, NY, USA;(4) Present address: Department of Physcis, Princeton University, 08544 Princeton, NJ, USA |
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Abstract: | We report a neutron scattering investigation of a La1.65Nd0.35CuO4 single crystal which undergoes a second order structural transition with decreasing temperature from a high temperature orthorhombic phase (space group Bmab) to a distinct low temperature orthorhombic phase (space group Pccn) atT
s
=76 K. The transition is induced by the softening of the phonon mode that involves rotations of the tilt axis of the CuO6 octahedra. Antiferromagnetic long range order is established belowT
N
=316 K, and a hysteretic reorientation to a noncollinear spin structure occurs belowT
s
. The low energy spin dynamics of La1.65Nd0.35CuO4 aboveT
s
are closely similar to those of stoichiometric La2CuO4; at 100 K the gaps for in-plane and out-of-plane polarized spin waves are 2.3 meV and 5 meV, respectively. Out-of-plane polarized magnons are little affected by the structural transition, but the gap for in-plane polarized magnons increases markedly belowT
s
. |
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Keywords: | |
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