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Reentrant Metal-Insulator Transition in Ca_{1-x}Eu_{x}B_{6}

100%

Glushkov V., Anisimov M., Baybakov R., Demishev S., Filippov V., Flachbart K., Kuznetsov A., Shitsevalova N., Sluchanko N.

vol. 126

issue 1

294-295

Resistivity, Hall and Seebeck effects have been studied on single crystals of Ca_{1-x}Eu_{x}B_{6} (0 ≤ x ≤ 1) at temperatures 2-300 K and in magnetic fields up to 8 T. An insulating ground state is found to be limited by narrow range of Eu doping 0.6 ≤ x ≤ 0.8. This region is characterized by an enhanced colossal magnetoresistance (CMR), which reaches values of ρ(0)/ρ(7T) > 10^{6} for x = 0.63 at T < 10 K. Decreasing of Eu content in Ca_{1-x}Eu_{x}B_{6} below x* ≈ 0.6 restores the metallic ground state with moderate resistivity (ρ ~ 1 ÷ 5 mΩ·cm) and CMR amplitude (ρ(0)/ρ(7T) < 7). The second metal-insulator transition (MIT) in Ca_{1-x}Eu_{x}B_{6} is observed beyond the whole conductivity region found earlier in the narrow range of Eu doping (0.7 ≤ x ≤ 0.8). The correlation between the enhanced CMR amplitude, the onset of positive diffusive thermopower and the elevation of anomalous Hall effect, determined for Eu content 0.6 ≤ x ≤ 0.85, favors the idea that a smooth change of band structure is the main factor governing the reentrant MIT in Ca_{1-x}Eu_{x}B_{6}.

Hall Effect in GdB_{6}

81%

Anisimov M., Bogach A., Glushkov V., Demishev S., Samarin N., Shitsevalova N., Levchenko A., Filippov V., Kuznetsov A., Flachbart K., Sluchanko N.

vol. 126

issue 1

348-349

The Hall effect of GdB_{6} has been studied on high quality single crystals in the temperature range 2-150 K and in magnetic field of 1 T. The obtained data allow to detect anomalies in the antiferromagnetic (AF) phase including (i) a drastic enhancement of negative Hall coefficient below T_{N1} ≈ 15.5 K and (ii) the appearance of an anomalous Hall effect at T_{N2} ≈ 4.7 K. Possible scenarios of the AF ground state formation are discussed.

Charge Transport and Magnetism in Eu_{1-x}Ca_{x}B_6

81%

Glushkov V., Anisimov M., Batko I., Batkova M., Bogach A., Demishev S., Filipov V., Flachbart K., Kuznetsov A., Sannikov I., Shitsevalova N., Sluchanko N.

issue 5

891-892

Transport, magnetic and thermal properties of substitutional solid solution Eu_{1 - x}Ca_{x}B_6 single crystals (0 ≤ x ≤ 0.244) have been studied at 1.8 ≤ T ≤ 300 K and in magnetic fields up to 8 T. Calcium doping is shown to result in a metal-insulator transition, which occurs at x_{MIT} ≈ 0.2. In vicinity of metal-insulator transition the effect of colossal magnetoresistance is found to be very sensitive to Ca content, the amplitude varying from Δ = [ ρ (0)- ρ (8T)]/ρ(8T) ≈1.4×10^2 to Δ ≈ 7.5 × 10^3 for 0.14 ≤ x ≤ 0.16. The analysis of magnetic contribution to heat capacity shows that a large amount of magnetic entropy ( ≈ 30%) releases in Eu_{0.845}Ca_{0.155}B_6 when moving from the Curie temperature T_{C} ≈ 5.5 K to the characteristic one T* ≈ 30 K. This observation as well as the large amplitude of low field colossal magnetoresistance effect and the deviation of magnetic susceptibility from the Curie-Weiss law detected for x = 0.155 compound in the interval T_{C} ≤ T ≤ T* seem to be associated with magnetic phase separation induced by Ca doping.

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3 Acta Physica Polonica A

2 2014

1 2010

3 Anisimov M.

3 Demishev S.

3 Flachbart K.

3 Glushkov V.

3 Kuznetsov A.

3 Shitsevalova N.

3 Sluchanko N.

2 Bogach A.

2 Filippov V.

1 Batko I.

1 Batkova M.

1 Baybakov R.

1 Filipov V.

1 Levchenko A.

1 Samarin N.

1 Sannikov I.

Search results

Reentrant Metal-Insulator Transition in Ca_{1-x}Eu_{x}B_{6}

Hall Effect in GdB_{6}

Charge Transport and Magnetism in Eu_{1-x}Ca_{x}B_6