Abstract
Monocrystalline CeCu2 has been studied by muon-spin rotation and relaxation(μSR) spectroscopy, using transverse- and longitudinal-field techniques between 5 and 300 K forthe paramagnetic state, and in zero field (ZF) for the ordered antiferromagnetic (AF) phase, K. As in the isostructural orthorhombic compoundsGdCu2 and PrCu2, in CeCu2 the μ+ is found at a 4e site. Bulk magnetic susceptibility and local susceptibility (extracted from theμ+ Knight shift) are found to differ, most probably because of a change in crystalline electric field splittingof the Ce3+ ions next to the muon. The relaxation of theμ+-spin polarization shows heavily anisotropic magnetic field fluctuations, explainedby a dominant moment fluctuation amplitude along the crystallographicb axis. BelowTN, ZF measurementsreveal a spontaneous μ+ precession frequency. The corresponding static magnetic fieldpattern is consistent with the known AF structure; fields at theμ+ and Ce momentsare parallel to the ± c axis. The temperature dependence of theμSR frequency isfitted by a two T-regime model, reflecting critical behaviour nearTN and magnonexcitation at low T. The oriented Ce moment values extracted from neutron diffraction measurements are not consistentwith the μSR results. Part of the discrepancy could possibly be explained by a change of the contact-hyperfine couplingparameter A0 at low temperature.
Published Version
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