title: Spin-driven phonon splitting in bond-frustrated ZnCr2S4.
abstract: Magnetic susceptibility, specific heat, thermal expansion, and IR spectroscopy provide experimental evidence that the two subsequent antiferromagnetic transitions in ZnCr2S4 at TN1 = 15 K and TN2 = 8 K are accompanied by significant thermal and phonon anomalies. The anomaly at TN2 reveals a temperature hysteresis typical for a first-order transformation. Because of strong spin-phonon coupling, both magnetic transitions at TN1 and TN2 induce a splitting of phonon modes. The anomalies and phonon splitting observed at TN2 are suppressed by strong magnetic field. Regarding the small positive Curie-Weiss temperature Theta approximately 8 K, we argue that this scenario of two different magnetic phases with different magnetoelastic couplings results from the strong competition of ferromagnetic and antiferromagnetic exchange.
authors.affiliation: Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, D-86159 Augsburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Hemberger
authors.forename: T
authors.initials: T
authors.lastname: Rudolf
authors.forename: H-A
authors.initials: HA
authors.lastname: Krug von Nidda
authors.forename: F
authors.initials: F
authors.lastname: Mayr
authors.forename: A
authors.initials: A
authors.lastname: Pimenov
authors.forename: V
authors.initials: V
authors.lastname: Tsurkan
authors.forename: A
authors.initials: A
authors.lastname: Loidl