High-field study of the magnetization in Ti doped ErCo2 compound

Abstract

The magnetization of powdered MgCu2 structure-type intermetallic ErCo1.95Ti0.05 was studied in the temperature range of 4.2–123K in magnetic fields up to 23T. A field-cooled magnetization jump at certain temperatures (TC) corresponds to a first-order magnetic phase transition from a paramagnetic to a ferrimagnetic state indicating cobalt moment formation. We observe that TC approach asymptotically T=50K with the cooling field Hc. The magnetization above TC stays constant (temperature independent), but does not saturate even in the field of 23T. The moment per unit formula was found to be approximately 7.25μB for this field. This behavior may be attributed to domain structures with the enhanced magnetocrystalline anisotropy field with titanium impurities. Magnetization versus magnetic field curves has also been recorded for both zero-field-cooled and field-cooled cases at various temperatures below and above TC. These curves below TC show typical ferrimagnetic phase; in the intermediate temperature range of 34–50K metamagnetism was observed and the sample becomes pure paramagnetic above 50K. In addition, the resistivity measurement was performed in the temperature range of 4.2–273K. A jumplike drop in the resistivity was observed at TC. In comparison with that of ErCo2, this transition temperature shifts to higher temperature as much as 2K, consistent with the slight increase of the lattice parameter. This drop in resistivity becomes much deeper presumably due to the internal magnetoresistance within the large domains. Analysis of the resistivity data in terms of spin fluctuations including s-d electron scattering and electron-phonon interaction reveals that T2 behavior becomes dominant in the temperature range of 34–50K where the magnetization data exhibit metamagnetism. Therefore, we assert based on both magnetization and resistivity results that the spin-fluctuation effects are driving force for the cobalt moment formations.