• Araujo, Jp
• Ibarra, Mr
• Morellon, L.
• Pereira, Am
• Correia, Fc
• Sousa, Jb
• Braga, Me
• Magen, C.
• Algarabel, Pa
• Pinto, Rp
• Teixeira, Jm

Abstract

Very detailed measurements of the electrical resistivity of Gd-5(Si0.1Ge0.9)(4) are here reported, with special emphasis on the vicinity of the first-order (magneto structural) martensitic transition which occurs at T-S similar to 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 10300 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 (Delta T similar to 4 K) below T-S, either in heating or cooling runs. Remarkably, this 'local reproducibility' (within AT) remains in spite of the significant resistance changes which occur outside the A T-range under thermal cycling. In particular the residual resistance systematically increases under thermal cycling, but the corresponding effect is absent in the AT 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.

Topics

• impedance spectroscopy
• resistivity