resumo
The static magnetization and dynamic susceptibility responses of the cluster system within a Griffiths phase of the magnetocaloric compound Tb5-xLaxSi2Ge2 (x = 0.075) have been investigated. A novel cluster-glass state within the Griffiths phase is formed at a characteristic freezing temperature where short-range ferromagnetic correlations set in the paramagnetic regime. Ferromagneticlike correlations are built up at around 155 K, which suddenly become frozen at a lower temperature similar to 140 K, thus in analogy with a reentrant spin glass behavior. The ac susceptibility near the freezing temperature follows a critical slowing down process characterized by tau(0) = 10(-13)s and dynamic exponents zv similar to 6 and beta similar to 0.4, similar to well-known spin glass systems. The nonlinear ac susceptibility analysis shows clearly the existence of a transition associated to the reentrant behavior. The origin of the intermediate cluster-glass phase inside the Griffiths phase is proposed to be the result of a combination of short-ranged RKKY intralayer positive exchange interactions between rare-earth Tb3+ ions and antiferromagnetic exchange between adjacent interlayers involving Si and Ge atoms in connection to the Tb(3+)atoms.
palavras-chave
NONLINEAR AC SUSCEPTIBILITY; SPIN-GLASSES; TRANSITION; BEHAVIOR
categoria
Materials Science; Physics
autores
Marcano, N; Algarabel, PA; Barquin, LF; Araujo, JP; Pereira, AM; Belo, JH; Magen, C; Morellon, L; Ibarra, MR
nossos autores
João Silva
Bolseiro de pós-DoutoramentoGrupos
agradecimentos
Work at the University of Zaragoza is supported by the Spanish Ministerio de Ciencia, Innovacion y Universidades MAT2017-82970-C2-2-R and Spanish DGA (Grant No. E26). Work at the University of Cantabria is supported by the Spanish Ministerio de Ciencia, Innovacion y Universidades MAT2017-83631-C3-R. J.H.B. would like to thank CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement.