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Dr. Noelia Marcano Aguado, Centro Universitario de la Defensa de Zaragoza – The Griffiths‐like phase in magnetocaloric 5:4 intermetallics – 10 de Junho 14:00

10 de junho:14:00 - 15:00


The R5T4 family of intermetallic compounds(R = rare earth element, T = Si, Ge) has been a subject of intensive research since discovery of the giant magnetocaloric effect (GMCE) near the magnetostructural transition in Gd5Si2Ge2 compound [1]. The physical properties of these compounds are usually intimately related to their layered crystal structure, and especially the concomitant magnetic and crystallographic transitions. As a result, strong magnetocaloric, magnetorestrictive, magnetoresistance, and other effects are commonly observed [2]. In addition to the high technological potential of these materials, the appearance of an exotic egime such as Griffiths‐like phases (GP) make them appealing candidates for fundamental studies [3] [4] [5]. The fascination stems from the fact that magnetic order appears in the paramagnetic (PM)state. GP is characterized by the pre‐formation of ferromagnetically ordered nanometric clusters at some temperature TG, well above that of long‐range magnetic ordering Tordering (either TC or TN). In this talk I will show our recent advances in understanding the GP in 5:4 materials. In the first part of my talk, I will describe our results about the magnetic relaxation of the clusters in the GP on Tb5Si2Ge2, where GP was reported for the first time. The use of key characterization techniques, such as linear and nonlinear magnetic ac susceptibility, have provided significant information about the spin dynamics of the clusters. The new aspect here is the observation of a novel cluster‐glass state within GP [6]. In the second part, I will focus on the effect of hydrostatic pressure on the short‐range magnetic correlations in 5:4 materials. The obtained pressure‐temperature phase diagrams (P‐T) suggest that the clusters in the GP maintain the structural character of the PM state [7].

[1] V. K. Pecharsky et al., Phys. Rev. Lett. 78, 4494 (1997).
[2] Y. Mudryk et al., Z. Anorg. Allg. Chem. 637, 1948‐1956 (2011).
[3] R. B. Griffiths, Phys. Rev. Lett. 23, 17 (1969).
[4] C. Magén et al., Phys. Rev. Lett. 96, 167201 (2006).
[5] A. M. Pereira et al., Phys. Rev. B 82, 172406 (2010).
[6] N. Marcano et al., Phys. Rev. B 99, 054419 (2019).
[7] N. Marcano et al., Phys. Rev. B 102, 174416 (2020).


10 de junho
14:00 - 15:00