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MA: Magnetismus
MA 20: Poster: Films(1-36) Transp(37-56) Ex.Bias(57-67) Spindyn(68-80) Micromag(81-95) Particle(96-109) Imag.+Surface(110-113) Spinelectr(114-122) Theory+Micromag(123-131) Spinstr+Aniso(132-142) MagMat(143-156) Meas(157,158) MolMag+Kondo(159-162) Postdead(163-)
MA 20.144: Poster
Dienstag, 28. März 2006, 15:15–19:15, P1
Transport and thermodynamic properties of rare-earth transition-metal magnetism — •I. Klassen1, K. Berggold1, H. Hartmann1, O. Heyer1, S. Jodlauk1, K. Kordonis1, T. Lorenz1, A. Freimuth1, T. Fickenscher2, and R. Pöttgen2 — 1II. Phys. Inst., Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany — 2Anorg.-Chem. Inst., Universität Münster, Wilhelm-Klemm-Str. 8, D-48149 Münster, Germany
We present a study of the magnetoresistance, the magnetization, the specific heat, and the magnetocaloric effect of equiatomic RETMg intermetallics with RE=La,Eu,Gd,Yb and T=Ag,Au and of GdAuIn. Depending on the composition these compounds are paramagnetic (RE=La,Yb) or they order either ferro- or antiferromagnetically with transition temperatures ranging from about 13 to 81 K. All of them are metallic, but the resistivity varies over 3 orders of magnitude. We find pronounced magnetoresistance effects around the ordering temperature. The magnetic ordering leads also to well-defined anomalies in the specific heat. An analysis of the entropy change leads to the conclusions that generally the magnetic transition can be described by an ordering of localized S=7/2 moments arising from the half-filled 4f7 shells of Eu2+ or Gd3+. The magnetocaloric effect is weak for the antiferromagnets and rather pronounced for the ferromagnets for low magnetic fields around the zero-field Curie temperature. The antiferromagnetic order of GdAuIn can be suppressed in a field about 15 T. Furthermore GdAuIn shows a new phase boundary inside the antiferromagnetic phase.
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