Abstract
dc magnetization, ac magnetic susceptibility, magnetic relaxation, electrical resistivity and x-ray powder-diffraction studies of compound have been carried out in the temperature range of . The compound orders ferromagnetically at , followed by another transition at . This transition at is marked by a significant hysteresis in low applied fields in zero-field-cooled and field-cooled magnetization data. The saturation magnetic moment is at in a field, indicating the presence of strong crystalline electric fields. A signature of weak glassy behavior is observed below in frequency dependent ac magnetic susceptibility measurements. This observation is attributed to competing single-ion anisotropies of and ions that are statistically distributed in the lattice, thus creating large positional entropy. The paramagnetic phase of this compound includes a narrow region of Griffiths-phase-like behavior, signified by the presence of short-range ferromagnetic correlations. A long-time logarithmic relaxation of magnetization has been observed in the ferromagnetically ordered state. The electrical resistivity shows a slope change near and also a drop at . The electrical resistivity in the ferromagnetic state follows law, indicating the dominant role of magnon scattering. The magnetoresistance is at in a field. The role of quadrupolar interactions and magnetoelastic coupling in producing a possible structural distortion at has been considered and x-ray-diffraction studies were carried out down to . No structural change has been detected at , and hence the quadrupolar coupling between the rare-earth ions via the lattice should be weak, whereas direct higher-order Coulombic interactions may prevail.
3 More- Received 27 February 2007
DOI:https://doi.org/10.1103/PhysRevB.76.014407
©2007 American Physical Society