Charge Transport and Magnetism in Eu1 - xCaxB6

V. Glushkova,b, M. Anisimov b, I. Batko c, M. Batkova c, A. Bogach a, S. Demisheva,b V. Filipov d, K. Flachbart c, A. Kuznetsov e, I. Sannikov e, N. Shitsevalovad and N. Sluchanko a aA.M. Prokhorov General Physics Institute of RAS, 38, Vavilov str., Moscow 119991 Russia bMoscow Institute of Physics and Technology, 9, Institutskii per., Dolgoprudny, Moscow Region 141700, Russia cInstitute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 040 01 Košice, Slovak Republic dI. Frantsevich Institute for Problems of Materials Science, NAS, 3, Krzhyzhanovsky str., Kiev 03680, Ukraine eMoscow Engineering Physics Institute, 31, Kashirskoe Shosse, Moscow 115409, Russia

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Transport, magnetic and thermal properties of substitutional solid solution Eu1 - xCaxB6 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 xMIT ≈ 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 Δp = [ ρ (0)- ρ (8 T)]/ρ(8 T) ≈1.4×102 to Δp ≈ 7.5 × 103 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 Eu0.845Ca0.155B6 when moving from the Curie temperature TC ≈ 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 TC ≤ T ≤ T* seem to be associated with magnetic phase separation induced by Ca doping.

DOI: 10.12693/APhysPolA.118.891 PACS numbers: 71.30.+h, 75.30.Cr, 75.40.-s, 75.47.Gk