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Münster 1999 – scientific programme

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AM: Magnetismus

AM 17: Magnetische Phasenüberg
änge in drei- und niederdimensionalen Strukturen

AM 17.5: Talk

Thursday, March 25, 1999, 11:30–11:45, F4

Magnetoresistance in a low–carrier density ferromagnet: The case of EuB6 — •S Süllow1, I. Prasad2, S. Bogdanovich2, M.C. Aronson2, J.L. Sarrao3, and Z. Fisk31MPI Chemische Physik fester Stoffe, Dresden, Germany — 2University of Michigan, Ann Arbor, Michigan, USA — 3National High Magnetic Field Lab., Tallahassee, Florida, USA

We present a study of the magnetoresistivity of the low–carrier density ferromagnet EuB6. In this material we observe two ferromagnetic transitions at Tc1 = 15.3 K and Tc2 = 12.7 K in the resistivity. The upper transition is accompanied by a pronounced maximum of ρ, while the lower transition is represented by a broad shoulder on top of a rapidly decreasing ρ. The magnetoresistivity Δ ρ / ρ consists of two major contributions: a negative from the reduction of magnetic scattering in fields, dominant at lower fields and larger temperatures (above approx Tc1/2) and a positive metallic magnetoresistance at low temperatures and larger fields. The largest negative magnetoresistance is observed right at Tc1; here, fields of a few hundred Gauss are sufficient to wipe out the maximum in ρ. We discuss the different magnetoresistive regimes of EuB6, with particular emphasis on the mechanisms that lead to the removal of magnetic scattering in applied fields and compare our results to recent theoretical work on the magnetoresistance in low–carrier density ferromagnets [1].
P. Majumdar and P. Littlewood, PRL 81 (1998) 1314, Nature 395 (1998) 479

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