Magnetothermopower and magnetoresistivity ofRuSr2Gd1−xLaxCu

Abstract

We report measurements of magnetothermopower and magnetoresistivity as a function of temperature on RuSr 2 Gd 1-x La x Cu 2 O 8 (x = 0, 0.1). The normal-state thermopower shows a dramatic decrease after applying a magnetic field of 5 T, whereas the resistivity shows only a small change after applying the same field. Our results suggest that RuO 2 layers are conducting and the magnetic field induced decrease of the overall thermopower is caused by the decrease of partial thermopower associated with the spin entropy decrease of the carriers in the RuO 2 layers.

Memory effects in photoinduced femtosecond magnetization rotation in ferromagnetic GaMnAs

“…Due to the hole-mediated effective exchange interaction between Mn spins, the anisotropy fields in GaMnAs result from the coupling of several valence bands by the spin-orbit interaction and depend on the transient hole distribution and coherences between different bands [16]. In the static case, recent experimental [17] and theoretical [18] investigations have shown that increasing the hole density significantly reduces the cubic anisotropy (K c ) along the [100] direction, while enhancing the uniaxial anisotropy (K u ) along [1][2][3][4][5][6][7][8][9][10]. One therefore expects that the photoexcited hole population turns on an effective magnetic field pulse (∆B c ) along the [1][2][3][4][5][6][7][8][9][10] direction [ Fig.…”

Charge and Magnetization Inhomogeneities in Diluted Magnetic Semiconductors

“…Equation (9) shows that this is the case for high dielectric constant, small spin stiffness, strong dependence of T c on carrier concentration, and rapid onset of magnetization below T c . For Ga; MnAs, we estimate T by comparing experiments [7,9] to mean-field theory for homogeneous magnetization [14] and to spin-wave theory [18]. We find T c ÿ T of the order of 10 K. The properties of Ga; MnAs vary strongly with Mn concentration and growth procedures.…”

“…In Ref. [9], 5:4 10 5 K A 3 , which was used for the above estimate, whereas in Ref. [7], 1:5 10 5 K A 3 , which would increase T c ÿ T .…”

“…Since the magnetic interaction is mediated by the carriers, the magnetization and the Curie temperature increase for increasing carrier concentration [5][6][7][8][9][10]. In fact, the magnetization can be changed in situ by tuning the carrier concentration with a gate voltage [5,6,8].…”

Spin Dynamics in (III,Mn)V Ferromagnetic Semiconductors: The Role of Correlations

“…When treating correlations in the realistic (III,Mn)V system, the numerical solution of the above closed system of equations of motion is complicated by the coupling of many momenta and bands and by unsettled issues regarding the role on the dynamical and magnetic anisotropy properties of impurity bands, strain, localized states, and sp-d hybridization [1,20,21,22,23]. In the simpler RPA case, which neglects inelastic effects, a sixband effective mass approximation [16] revealed an order of magnitude enhancement of D. The single-band RPA model [15] also predicts maximum D at very small hole concentrations, while in the six-band model D increases and then saturates with hole doping.…”