Abstract
Antiferromagnetically (AFM) linked Heisenberg spins are found to be extremely frustrating in the Gd2Ti2O7 pyrochlore lattice because of the minimization exchange energy. The influence of the Ho3+substitution at Gd3+ site on the structural and magnetic of (Gd1−yHoy)2Ti2O7 (y = 0.0, 0.2, 0.4 and 0.6) single phasic cubic pyrochlore oxides have been investigated. Structural evaluation has proven that cubic pyrochlore (impurity-free) crystals with a cell parameter that continuously shrinkage and justifies Vegard rule. Raman spectroscopy studies exhibit that Ho3+ was completely absorbed in the Gd2Ti2O7 host matrix without substantially affecting its structural integrity. Reduction in the crystallite size and shifts in position of Raman active modes with magnetic Ho substitution is validated by the deterioration in structural ordering of the produced specimens. Observation on the increase in Curie Weiss temperature (θCW = –9.13 to +0.14 K) and effective magnetic moment (μeff/f.u. = 3.64–4.56 μB) on Ho doping leads to enhancement of ferromagnetic feature of the materials. But, spin glassy pattern has not been detected in all compositions. Thus, magnetic studies demonstrate that the system becomes less AFM character due to generation of ferromagnetic interaction among Gd–Ho (Ho–Ho) spins and disrupted network of Gd3+ ions by increase in chemical pressure in Gd2Ti2O7. Moreover, measured values of Msat are found to lower with rise in chemical pressure of the (Gd1−yHoy)2Ti2O7 system owing to the effects of particle angular averaging and single ion anisotropy.
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