title: Lattice strain accompanying the colossal magnetoresistance effect in EuB6.
abstract: The coupling of magnetic and electronic degrees of freedom to the crystal lattice in the ferromagnetic semimetal EuB(6), which exhibits a complex ferromagnetic order and a colossal magnetoresistance effect, is studied by high-resolution thermal expansion and magnetostriction experiments. EuB(6) may be viewed as a model system, where pure magnetism-tuned transport and the response of the crystal lattice can be studied in a comparatively simple environment, i.e., not influenced by strong crystal-electric field effects and Jahn-Teller distortions. We find a very large lattice response, quantified by (i) the magnetic Grüneisen parameter, (ii) the spontaneous strain when entering the ferromagnetic region, and (iii) the magnetostriction in the paramagnetic temperature regime. Our analysis reveals that a significant part of the lattice effects originates in the magnetically driven delocalization of charge carriers, consistent with the scenario of percolating magnetic polarons. A strong effect of the formation and dynamics of local magnetic clusters on the lattice parameters is suggested to be a general feature of colossal magnetoresistance materials.
authors.affiliation: Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt (Main), SFB/TR49, Germany.
authors.forename: Rudra Sekhar
authors.initials: RS
authors.lastname: Manna
authors.affiliation: Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt (Main), SFB/TR49, Germany.
authors.forename: Pintu
authors.initials: P
authors.lastname: Das
authors.affiliation: Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt (Main), SFB/TR49, Germany.
authors.forename: Mariano
authors.initials: M
authors.lastname: de Souza
authors.affiliation: Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt (Main), SFB/TR49, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Schnelle
authors.affiliation: Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt (Main), SFB/TR49, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Lang
authors.affiliation: Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt (Main), SFB/TR49, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Müller
authors.affiliation: Department of Physics, Florida State University, Tallahassee, Florida 32306, USA.
authors.forename: Stephan
authors.initials: S
authors.lastname: von Molnár
authors.affiliation: Department of Physics, University of California, Irvine, California 92697, USA.
authors.forename: Zachary
authors.initials: Z
authors.lastname: Fisk