High temperature spin-freezing transition in pyrochlore Eu2Ti2O7: A new observation from ac-susceptibility

Highlights: • Details magnetic property study of geometrically frustrated pyrochlore Eu₂Ti₂O₇ has been investigated. • Ac susceptibility measurements revealed a clear spin freezing transition for this system for the first time. • The spin freezing at such a high temperature (35 K) is very surprising as well as interesting. • The study yields the underlying physics to be associated with single spin relaxation process. • Non-magnetic dilution also confirmed the presence of single spin freezing in this case. The magnetization (both dc and ac) of pyrochlore Eu₂Ti₂O₇ have been investigated. Ac susceptibility (χ^/ & χ^//) measurements reveal a new unusual spin freezing below 35 K for pure Eu₂Ti₂O₇. Frequency dependence of these ac χ^// peak positions indicate slow spin relaxation near this temperature and it follows the Arrhenius formula suggesting a thermally activated relaxation process. The origin of this spin freezing has been attributed essentially to a single ion process which is associated to Eu³⁺ spin relaxation. Non-magnetic dilution by Y³⁺ ions also confirms the single ion freezing.