A. V. Levchenko

Anomalies of magnetoresistance of compounds with atomic clusters RB12 (R = Ho, Er, Tm, Lu)

The magnetoresistance and magnetization of single-crystal samples of rare-earth dodecaborides RB12 (R = Ho, Er, Tm, Lu) have been measured at low temperatures (1.8–35 K) in a magnetic field of up to 70 kOe. The effect of positive magnetoresistance that obeys the Kohler’s rule Δρ/ρ = f(ρ(0, 300 K)H/ρ(0, T)) is observed for the nonmagnetic metal LuB12. In the magnetic dodecaborides HoB12, ErB12, and TmB12, three characteristic regimes of the magnetoresistance behavior have been revealed: the positive magnetoresistance effect similar to the case of LuB12 is observed at T > 25 K; in the range TN ≤ T ≤ 15 K, the magnetoresistance becomes negative and depends quadratically on the external magnetic field; and, finally, upon the transition to the antiferromagnetic phase (T < TN), the positive magnetoresistance is again observed and its amplitude reaches 150% for HoB12. It has been shown that the observed anomalies of negative magnetoresistance in the paramagnetic phase can be explained within the Yosida model of conduction electron scattering by localized magnetic moments. The performed analysis confirms the formation of spin-polaron states in the 5d band in the vicinity of rare-earth ions in paramagnetic and magnetically ordered phases of RB12 and makes it possible to reveal a number of specific features in the transformation of the magnetic structure of the compounds under investigation.

Antiferromagnetic instability and the metal-insulator transition in Tm1 − xYbxB12 rare earth dodecaborides

The magnetic and transport characteristics of substitutional solid solutions of the Tm1−xYbxB12 rare earth dodecaborides have been investigated. The measurements performed in the wide temperature range 1.8−300 K on the high-quality single-crystalline samples make it possible to conclude that as x increases, antiferromagnetic instability develops with the quantum critical point (TN = 0) near x = 0.3 and relevant dielectrization of the electron structure in the range 0 ≤ x ≤ 0.8 takes place. With the results of the thermoelectric measurements in Tm1−xYbxB12, the activation energy values and their dependence on x have been determined.

Charge transport in HoxLu1-xB12: Separating Positive and Negative Magnetoresistance in Metals with Magnetic Ions

The magnetoresistance (MR)

Specific heat of CexLa1 − xB6 in the low cerium concentration limit (x ≤ 0.03)

\Delta \rho/\rho

Electronic Raman scattering and the renormalization of the electron spectrum in LuB12

of cage-glass compound Ho

Specific features of magnetoresistance during the antiferromagnet—paramagnet transition in Tm1 − xYbxB12

_x

Separation of the contributions to the magnetization of Tm1 − xYbxB12 solid solutions in steady and pulsed magnetic fields

Lu

Enhancement of the colossal magnetoresistance in Eu1 − xCaxB6

_{1-x}

Bulk and local susceptibility of RB12 (R – Ho, Er, Tm)

B

Transport properties of variously doped SmB6

_{12}