Short-range ferromagnetism and spin-glass state in Y0.7Ca0.3MnO3 - art. no. 174405

Dynamic magnetic properties of Y0.7Ca0.3MnO3 are reported. The system appea rs to attain local ferromagnetic order at T(SRF)approximate to 70 K, where SRF is short-range ferromagnetism. Below this temperature the low-held magn etization becomes history dependent, i.e., the zero-field-cooled (ZFC) and field-cooled magnetization deviate from each other and close logarithmic re laxation appears at our experimental time scales (0.3-10(4) sec). The zero- field-cooled magnetization has a maximum at T(f)approximate to 30 K, wherea s the field-cooled magnetization continues to increase, although less sharp ly, also below this temperature. Surprisingly, the dynamics of the system s how nonequilibrium spin-glass features not only below the maximum in the ZF C magnetization, but also in the temperature region between this maximum an d T-SRF. The aging and temperature cycling experiments show only quantitati ve differences in the dynamic behavior above and below the maximum in the Z FC magnetization; similarly, memory effects are observed in both temperatur e regions. We attribute the high-temperature behavior to the existence of c lusters of short-range ferromagnetic order below T-SRF; the configuration e volves into a conventional spin-glass state at temperatures below T-f.