Magnetostructural properties ofHo5(Si0.8Ge0.2)

Abstract

The magnetostructural properties of Ho 5 ͑Si 0.8 Ge 0.2 ͒ 4 have been investigated both experimentally and by using first-principles theory. The compound orders ferromagnetically at 50 K, and in the temperature range of 50-100 K it exhibits a Griffiths phaselike behavior. The dc magnetization, heat capacity, and the relaxation and frequency dependence of the ac susceptibility indicate that the long-range magnetic order and a spin-glasslike state may coexist in Ho 5 ͑Si 0.8 Ge 0.2 ͒ 4 over a certain temperature range below T C . Despite adopting the Gd 5 Si 2 Ge 2 -type monoclinic ͑M-type͒ structure at room temperature, the compound does not exhibit a magnetostructural transition at T C , unlike some other members of the R 5 ͑Si 1−x Ge x ͒ 4 series with R = Gd, Tb, and Dy. The tight-binding linear muffin-tin orbital calculations within the local spin-density approximation show that in R 5 ͑Si 1−x Ge x ͒ 4 compounds the gain in the exchange energy brought about by the M-type to Gd 5 Si 4 -type orthorhombic ͑O-I͒ transformation decreases as R is changed from Gd to other heavy lanthanides and the absence of the M to O-I phase transformation in Ho 5 ͑Si 0.8 Ge 0.2 ͒ 4 is a result of low gain in the magnetic contribution to the total energy.

Griffiths-like phase of magnetocaloricR5(SixGe1−x)Pereira1, Morellón2, Magén3 et al. 2010Phys. Rev. B526390View full textAdd to dashboardCite

“…In the case of Ho 5 ͑Si x Ge 1−x ͒ 4 , the magnetic properties were recently reported in Ref. 30, it was also found the existence of SRMC in the PM phase confirmed by the recent work performed by Singh et al 25 The extended ͑x , T͒ phase diagram is depicted in Fig. 2͑d͒.…”

“…24͒ and also, very recently, on Ho 5 SiGe 3 . 25 Inelastic neutron-scattering studies in Tb 5 Ge 4 have been carried out to infer about the origin of such short-range correlations. [26][27][28] Previous works on Gd 5 ͑Si x Ge 1−x ͒ 4 established that the Griffiths phase arises from the onset of spin clusters at the temperature of the un-diluted magnetic phase ͑the critical temperature expected if the structure remains unchanged͒, identified as the O͑I͒.…”

R5T4 Compounds

“…The temperature-dependent X-ray powder diffraction experiment confirmed that the crystal structure of Ho 5 Si 3.2 Ge 0.8 remains monoclinic below T C ¼ 50 K, in the ferromagnetic state. The magnetocaloric effect is moderate (DT ad ¼ 1.3 K for the DH ¼ 20 kOe) and exhibits a plateau-like behavior between $20 and 50 K (Singh et al, 2010b). Metastability of the low-temperature magnetization data, frequency dependence of the ac magnetic susceptibility, and strong magnetic relaxation behavior were found to coexist with the long-range ferromagnetic order in the extended temperature range below T C .…”

“…Structural, magnetic, and thermodynamic properties of the monoclinic Ho 5 Si 3.2 Ge 0.8 phase (Gd 5 Si 2 Ge 2 type) have been examined in detail by Singh et al (2010b). The temperature-dependent X-ray powder diffraction experiment confirmed that the crystal structure of Ho 5 Si 3.2 Ge 0.8 remains monoclinic below T C ¼ 50 K, in the ferromagnetic state.…”

Structure, magnetic and magnetocaloric properties of RE11Ge8In2 (RE = Gd–Tm)

“…While only detailed temperature-dependant neutron studies can clarify the magnetic structure of the Tb-, Dy-and Hocontaining phases, the available data suggests that a spin reorientation is likely to occur below the Curie temperatures. Spin reorientation is often observed in the rare-earth containing phases [17e19] and it can be viewed as magnetic frustration resulting from a long-range oscillatory nature of the RudermaneKitteleKasuyaeYosida (RKKY) interactions and presence of the various REeRE bonds [20]. The Curie temperatures, T C , range from 10 to 84 K and they decrease from Gd to Tm, with the exception of Tb (Table 4).…”