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. Fisk3 — 1MPI 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