Pressure and Magnetic Field Effects on Electrical Resistivity and Thermopower of Y_1-xTb_xCo₂ System

Effects of pressure and magnetic field on transport properties of Y1−xRxCo2alloys (R=Gd, Tb, Dy, Ho and Er)

“…The latter feature means that, contrary to common expectation, the external magnetic field enhances static magnetic disorder in the ferromagnetic system in its ground state. This unusual characteristic behavior was observed also in other Y 1−x R x Co 2 (R=Tb, Dy, Ho and Er) alloys [5,6]. The anomalous behavior of the low temperature conduction in Y 1−x R x Co 2 was explained by the interplay of metamagnetic instability of Co 3d itinerant electrons and structural disorder in the R sublattice, which induces a spatially random distribution of high and low Co 3d magnetization, leading to a partially ordered state of the 3d itinerant electron system [4,6].…”

“…Residual resistivity of the alloys ρ 0 rapidly increases with increasing x and attains a maximum value near x c , where MR and PR change their sign. At the maximum ρ 0 constitutes about 70% of the room-temperature value of total resistivity of the alloy [4,5,6]. Figure 1 depicts the magnetic filed (ρ(B)) and pressure (ρ(P )) dependencies of resistivity of Y 0.82 Gd 0.18 Co 2 alloy (x c = 0.12 for Y 1−x Gd x Co 2 system).…”

“…Both, ρ(B) and ρ(P ), measured at T =2 K, show almost linear variations with magnetic field or pressure, respectively. From the model developed in our previous papers [4,6], we can obtain the following relations:…”

Pressure and Substitution Effects on Transport and Magnetic Properties of Y1-xRxCo2Systems with Static Magnetic Disorder

“…Moreover, an unusual positive magnetoresistance and a strong pressure effect on resistivity have been observed in the magnetically ordered region at x > x c . 10,11,[14][15][16] In previous papers, we proposed a theoretical model that explains the anomalous variations of low-temperature conduction with composition x, magnetic field B, and pressure P in Y 1Àx R x Co 2 alloys. 10,[16][17][18] A random distribution of magnetic R and nonmagnetic Y ions over the rare-earth sublattice in Y 1Àx R x Co 2 alloys creates spatially fluctuating effective field B eff ðrÞ ¼ B þ n fd M R ðrÞ acting on the 3d electron subsystem [here, B is the external magnetic field, M R ðrÞ the 4f magnetic moment at site r of the rare-earth sublattice, and n fd the 3d-4f exchange constant].…”

“…This field can be characterized by the distribution function FðB eff Þ. 10,16) The spatially fluctuating B eff induces, in a certain range of alloy compositions, a nonhomogeneous magnetic state of the Co-3d electron subsystem: as x decreases, the mean value of B eff shifts to lower fields, and in a certain range of x, FðB eff Þ essentially has a nonzero weight for both B eff < B c and B eff > B c . Here, B c is the critical magnetic field of the metamagnetic transition of the Co 3d electron subsystem.…”