Multi-step and anomalous reproducible behaviour of the electrical resistivity near the first-order magnetostructural transition of Gd₅(Si_0.1Ge_0.9)₄

Abstract

Very detailed measurements of the electrical resistivity of Gd 5 (Si 0.1 Ge 0.9 ) 4 are here reported, with special emphasis on the vicinity of the first-order (magnetostructural) martensitic transition which occurs at T S ∼ 87 K. The data cover more than fifty thermal cycles spanning the temperature ranges of 300-10 K (long cycles) and 105-10 K (short cycles). In the initial 10-300 K cycles the martensitic transition takes place in three closely-spaced steps, with associated resistance (R) discontinuities and large thermal hysteresis. In a subsequent series of short cycles (10-105 K) a unique transition occurs, exhibiting a common and quite reproducible R(T ) behaviour within a small temperature range ( T ∼ 4 K) below T S , either in heating or cooling runs. Remarkably, this 'local reproducibility' (within T ) remains in spite of the significant resistance changes which occur outside the T -range under thermal cycling. In particular the residual resistance systematically increases under thermal cycling, but the corresponding effect is absent in the T temperature range. This excludes microcracking as a dominant resistive mechanism in our results, pointing to an intrinsic character of the reproducible behaviour just below T S . We also analyse the R(T ) behaviour when changing from long to short thermal cycles, and the R(T ) evolution towards a reversible final behaviour, after extended thermal cycling.

Transport and magnetic properties of the Er5Si4 compound

“…Due to the breaking of the covalent bonds at this transition, and corresponding changes in the number of carriers, transport properties show very distinct features as already reported in previous work [9,10].…”

Suppression of magnetostructural transition on GdSiGe thin film after thermal cyclings

“…In the R5(Si,Ge)4 family of bulk compounds, we highlight the works from Casanova and co-authors and Perez and co-authors which demonstrate that the metastability, responsible for the thermal hysteresis, is reduced when the number of thermal cycles increases 23,33 . Furthermore, a previous study on the electrical resistivity behavior has also shown a thermal hysteresis area reduction as the number of cycles for Gd5(Si0.1Ge0.9)4 20,21 increases: the number of defects, the spin disorder, domain reorientation or the preferential Si/Ge sites were assigned as the major causes leading to the metastability reduction. The local behavior of the magnetic relaxation (across the field increase and decrease) of the Gd5Ge4 first-order transition has also been investigated 34 .…”

“…Also, properties such as electrical resistance [18][19][20][21] , thermopower 22 and specific heat 23 have been reported as dependent of thermal cycling on Gd5(SixGe1-x)4 alloys. However, all studies performed on these compounds have been focused in the bulk form or in micrometric scale samples.…”

“…during heating, a significant increase in the unit cell volume will lead to a stress increase arising from the volume cell expansion, thus originating the arrest of the structural transition. In fact, this mechanism has been referenced several times for the bulk materials to explain changes in their properties, namely morphological, magnetic and transport 21 . Also the same explanation was used for other family of systems showing drastic volume changes 25 .…”

Electron scattering processes in Ho5(SixGePereira1, Araújo2, Peixoto3 et al. 2011Phys. Rev. B9050View full textAdd to dashboardCite

“…This polarization affects the electron energy states (and scattering) leading to an anomalous behavior in the electrical resistivity ρ(T ). [23][24][25] We highlight that this type of measurement was a vital technique for the discovery of the training effect in these materials. [24][25][26] Furthermore, an insulating-like behavior near the Néel temperature (T N ) was observed.…”