Regensburg 2002 – scientific programme

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MA: Magnetismus

MA 10: Poster : Dünne Schichten(1-21),Spinabh.Transp.(22-39),Exch.Bias(40-51),Spindyn.(52-55),Mikromag.(56-66),Partikel(67-74),Abb.Verf.(75-77),Oberfl.+Spinelektr.+Elektr.Theo+Mikromag(75-87),PÜ+Aniso+Werkst/Leg.(88-103),Mol.Mag.+N-dim+Messm.+Postdead(104-111

MA 10.38: Poster

Tuesday, March 12, 2002, 15:00–19:00, Bereich A

Magnetoresistive measurements of MnAu₂ melt-spun alloys with Fe additions at high pulsed fields — •N. Kozlova, A. Handstein, D. Eckert, U.-K. Rößler, M. Kozlov, K.-H. Müller, and L. Schultz — IFW Dresden, Postfach 270116, 01171 Dresden

A magnetoresistance (MR) measurement technique has been developed for a pulsed-field facility with fields up to 50 Tesla generated by a solenoid with rise time of about 10 ms. Measurements based on a software digital signal processing Lock-In method are performed by using four-point probe technique and ac current through the sample. Melt-spun ribbons of Mn_1−xFe_xAu₂ (x=0, 0.01, 0.02, 0.05, 0.075) have been investigated at different temperatures between 10 K and 300 K. The parent compound MnAu₂ shows a (negative) giant MR effect at 10 K related to a helimagnetic to ferromagnetic transition in external magnetic fields. Fe substitution suppresses the helimagnetism, therefore, reduces the negative MR, and induces a ferromagnetic behavior at higher substitution x>=0.05. At high fields and low temperature a re-increase of MR and eventually a positive MR is found for all samples. This effect, possibly related to increased s-d electronic scattering due to band distortion, is enhanced in Fe substituted samples and leads, e.g., to a positive MR about 700% for x=0.05 at 30 Tesla and at 10K.

The work is supported by the BMBF project 03 SC5 DRE.