Magnetic disorder in Ti doped ErCo2: High-magnetic-field study


Oener Y. , GUILLOT M.

JOURNAL OF APPLIED PHYSICS, vol.105, no.7, 2009 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 105 Issue: 7
  • Publication Date: 2009
  • Doi Number: 10.1063/1.3070625
  • Title of Journal : JOURNAL OF APPLIED PHYSICS

Abstract

Magnetization measurements have been carried out on ErCo(2-x)Tix (x=0, 0.01, 0.02, 0.03, 0.04, and 0.05) alloys in the temperature range of 4-300 K under high dc magnetic fields of up to 23 T. The substitution of Ti for Co causes no change in the crystal structure of ErCo2 (cubic Laves phase C15 with space group Fd (3) over barm). The lattice parameter a decreases almost linearly with increasing x up to x=0.04 and then increases slightly for the largest Ti concentration. The Curie temperature T-C shows a similar change with Ti concentration. Above T-C all the studied samples show a small but unambiguous hysteresis associated with a metamagnetic transition. The observed hysteresis is attributed to the coexistence of the paramagnetic and the field-induced ferrimagnetic states. Linear temperature extrapolations of the critical fields H-c1 (where the hysteresis sets in) and H-c2 (the highest field where the hysteresis is observed) were done for each sample. Two different critical temperatures were found suggesting the existence of Co clusters. Indeed, weak negative magnetization values in low fields at low temperatures were observed for zero-field-cooling magnetic measurements. The negative magnetization is also attributed to the existence of Co clusters above T-C. The spontaneous magnetization values M-s of the samples were deduced as a function of Ti concentration from the high-field data. M-s passes through a maximum for the x=0.03 sample with a maximum value of 7.15 mu(B) (6.30 mu(B) in pure ErCo2). We show how a decrease in the Er-Co antiferromagnetic exchange coupling with Ti doping may lead to such an observed maximum. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3070625]