Rhombohedral shaped, single crystal hematite particles ( = 93 nm) with narrow size distribution were prepared by hydrolysis of iron chloride and polymerisation in water. The results of field dependent magnetization measurements at different warming(W)/cooling(C) rate, and AC susceptibility measurements at variable frequency are reported and discussed. Thermal hysteresis associated to the Morin transition and field dependence of the Morin temperature (TM) are observed in warming-cooling cycles (TM = 25 K and 13 K for H = 0.1 T and 3 T, respectively) due to the first order phase transition. A frequency dependence of AC susceptibility is observed above TM, as a result of the relaxation of the magnetic moment of hematite particles in the weak-ferromagnetic phase.
THERMAL HYSTERESIS OF MORIN TRANSITION IN HEMATITE PARTICLES / Suber, L.; Imperatori, P.; Mari, A.; Marchegiani, G.; VASQUEZ MANSILLA, M.; Fiorani, D.; Plunkett, W. R.; Rinaldi, D.; Cannas, C.; Ennas, G.; Peddis, D.. - In: PHYSICAL CHEMISTRY CHEMICAL PHYSICS. - ISSN 1463-9076. - 12:(2010), pp. 6984-6989. [10.1039/B925371H]
THERMAL HYSTERESIS OF MORIN TRANSITION IN HEMATITE PARTICLES
D. RINALDI;
2010-01-01
Abstract
Rhombohedral shaped, single crystal hematite particles ( = 93 nm) with narrow size distribution were prepared by hydrolysis of iron chloride and polymerisation in water. The results of field dependent magnetization measurements at different warming(W)/cooling(C) rate, and AC susceptibility measurements at variable frequency are reported and discussed. Thermal hysteresis associated to the Morin transition and field dependence of the Morin temperature (TM) are observed in warming-cooling cycles (TM = 25 K and 13 K for H = 0.1 T and 3 T, respectively) due to the first order phase transition. A frequency dependence of AC susceptibility is observed above TM, as a result of the relaxation of the magnetic moment of hematite particles in the weak-ferromagnetic phase.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
