title: Unconventional magnetostructural transition in CoCr2O4 at high magnetic fields.
abstract: The magnetic-field and temperature dependencies of the ultrasound propagation and magnetization of single-crystalline CoCr(2)O(4) have been studied in static and pulsed magnetic fields up to 14 and 62 T, respectively. Distinct anomalies with significant changes in the sound velocity and attenuation are found in this spinel compound at the onset of long-range incommensurate-spiral-spin order at T(s)=27  K and at the transition from the incommensurate to the commensurate states at T(l)=14  K, evidencing strong spin-lattice coupling. While the magnetization evolves gradually with the field, steplike increments in the ultrasound clearly signal a transition into a new magnetostructural state between 6.2 and 16.5 K and at high magnetic fields. We argue that this is a high-symmetry phase with only the longitudinal component of the magnetization being ordered, while the transverse helical component remains disordered. This phase is metastable in an extended H-T phase space.
authors.affiliation: Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany and Institute of Applied Physics, Academy of Sciences of Moldova, MD 2028 Chisinau, Republic of Moldova.
authors.forename: V
authors.initials: V
authors.lastname: Tsurkan
authors.affiliation: Hochfeld-Magnetlabor Dresden (HLD), Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Zherlitsyn
authors.affiliation: Hochfeld-Magnetlabor Dresden (HLD), Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Yasin
authors.affiliation: Institute of Applied Physics, Academy of Sciences of Moldova, MD 2028 Chisinau, Republic of Moldova.
authors.forename: V
authors.initials: V
authors.lastname: Felea
authors.affiliation: Hochfeld-Magnetlabor Dresden (HLD), Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden, Germany.
authors.forename: Y
authors.initials: Y
authors.lastname: Skourski
authors.affiliation: Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Deisenhofer
authors.affiliation: Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany.
authors.forename: H-A
authors.initials: HA
authors.lastname: Krug von Nidda
authors.affiliation: Hochfeld-Magnetlabor Dresden (HLD), Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Wosnitza
authors.affiliation: Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Loidl