Coherent Ferromagnetic Precipitate and Anomalies in the Heat Conduction and Thermopower of Mn_2-xCr_xSb Single Crystals

Abstract

The heat diffusivity D, the electrical resistivity p and the thermoelectric power S of tetragonal Μn2-x Crx Sb single crystals with 0.02 < x < 0.12 have been measured in the temperature range of 90 K< Τ < 350 K and along different crystal axes. The heat conductivity κ and σ = 1/p are anisotropic along the crystal axes a, c with a ratio of 2:1. κ(T), p(Τ) and S(Τ) show anomalies at the spin reorientation temperature TRm of the matrix (M) Μ n 2 -C r x S b , b u t a l s o a t t h a t o f t h e c o h e r e n t f e r r o m a g n e t i c p r e c i p i t a t e (P) Mn1.037Cr0.11Sb, ΤRP which is assigned to variations in the spin dependent scattering at the Μ/Ρ interfaces via changes in the relative orientation of the magnetization vectors of matrix and precipitate (spin valve effect).

Field Dependent Specific Heat Capacity of Mn2?xCrxSb Single Crystals

“…Stress related shifts only depend on H s and M s both of which can be considered approximately constant for T`240 K. Thus, the transport anomalies found at lower temperatures, designated X 1 Y X 2 Y F F F (Fig. 5) which are virtually independent of x and of the matrix state, have been explained that way [46,36]. If, however, spin clamping occurs in a larger volume, the X i would be observed also in the derivatives of volume properties, i.e.…”

“…This can be seen, if for example one [45,46] and applying the equilibrium condition dEadq 0, this yields [36] T À T r ÀH s M s a2a 1acos q X 9…”

The baric coefficient of resistance of Mn1.9Cr0.1Sb as measured by the double AC method

“…In that case, the first appearance of the other phase might be important for the design of a baroor magnetocaloric cycle. Mn 2−x Cr x Sb undergoes itinerant metamagnetic ferrimagnetic (Fr) to antiferromagnetic (AF) transition on cooling accompanied by significant change of the unit cell volume, electrical resistance, local Mn magnetic moment [5][6][7][8][9][10][11][12][13]. Thus, in this contribution we depict first data on Mn 2−x Cr x Sb, which has been considered to be a candidate for magnetocaloric cooling [3,14], in particular as some samples show only a very small thermal hysteresis together with reasonable entropy steps, …”