Onset of magnetism in Y_1 xGd_xCo₂: effect on the heat capacity and electrical resistivity

Abstract

Results of the electrical resistivity, magnetoresistance and specific heat measurements are presented for Y1−xGdxCo2 in the vicinity of the critical Gd concentration xc ≈ 0.15 for the onset of a long-range magnetic order. Pronounced maxima of the coefficient γ of the T-linear specific heat, Debye temperature and residual resistivity as a function of concentration are found to exist at x = 0.1, i.e. just below xc. These anomalies, together with the existence of a minimum on the temperature dependences of the electrical resistivity at 0 < x < 0.15, are ascribed to the substantial influence of localized spin density fluctuations induced by f–d exchange in the itinerant d-electron subsystem of Co. The maximal extra contribution to the residual resistivity Δρresmax in Y1−xRxCo2 pseudobinaries is found to depend on the critical concentration as well as on the type of R ions, while the value of Δγmax depends only on the critical concentration of R ions. The significant upturns on Cp/T versus T2 dependences observed in Y1−xGdxCo2 at 0 < x < 0.15 may be indicative of a non-Fermi-liquid behaviour of the d-electron subsystem caused by the partial substitution of Gd for Y.

Influence of hydrogen absorption on structural and electrical transport properties of Ho1−xMmxCo2 alloys

“…Usually, minima in the temperature dependence of ͑T͒ are associated with freezing of the magnetic moments of ferro/ferrimagnetic clusters in random directions. [25][26][27] An increasing extent of spin fluctuations and a probable instability of the R moments are also evidenced by low temperature specific heat measurements in the dilute R concentrations. 28 The variation of T C upon Mm substitution is shown in inset 2 of Fig.…”

Pressure effect on thermopower of alloy system

“…The FM compounds show anomalous large positive magnetoresistance (MR) at low temperatures, which sharply contradicts to theoretical predictions for magnetoresistance of ferromagnetic materials with respect to the sign as well as to the magnitude of the effect [3]. Furthermore, strong enhancement of low-temperature resistivity, coefficient g of the linear term in the specific heat and of Debye temperature Y D were observed for the compounds with the composition near to the phase boundary between the paramagnetic and ferromagnetic ground state [4]. The anomalous positive magnetoresistivity and the composition dependence of the low-temperature resistivity of the alloys were explained by an interplay of the metamagnetic instability of Co 3d itinerant electrons and structural disorder in R-sublattice, which brings about spatially random distribution of high and low 3d magnetization for the compounds with xt0:3 [2].…”

Effect of static and dynamic disorder on electronic transport inRCo2compounds:Ho(AlБурков1, Bauer2, Gratz3 et al. 2008Phys. Rev. B11060View full textAdd to dashboardCite

“…As in the case of the above discussed Co localization, disorder and metamagnetism of the magnetic Co subsystem are the natural candidates. Baranov et al 36,37 were probably the first to emphasize the important role which disorder can play in RCo 2 -based alloys. In a certain range of alloy composition, 3d magnetic subsystem can be in "partially" ordered ground state, i.e., in the alloy there are spatial regions with high and low 3d magnetization.…”