Browsing by Author "Prokes, K"
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- ItemMagnetic order in YbMn2Si2 - neutron scattering investigation(Springer, 2013-08-01) Campbell, SJ; Hofmann, M; Mole, RA; Prokes, K; Wallacher, D; Wang, JLSeveral mechanisms have been proposed to account for the structural and magnetic behaviour of the rare earth intermetallic compound YbMn2Si2 below the transition that occurs around ∼30 K. We have carried out detailed neutron diffraction measurements over the temperature range ∼0.3–52 K and confirm both an antiferromagnetic structure with ferromagnetic Mn (001) planes coupled antiferromagnetically along the c-axis above ∼30 K and the absence of ordering of the Yb sublattice down to 0.3 K. The decrease in intensity of the (111) reflection around ∼30 K together with the appearance of satellite reflections of propagation vector k=0012 confirm that the magnetic unit cell doubles along the c axis below T N2. The resultant molecular field acting on half of the ions below ∼30 K removes the degeneracy of the Kramers doublets of the Yb3+ ions and accounts for the additional excitations observed below ∼30 K compared with the inelastic neutron scattering above ∼30 K. © 2013, The Korean Physical Society.
- ItemNeutron study of the magnetism in NiCl2•4SC(NH2)2(IOP Publishing Ltd., 2013-05-29) Tsyrulin, N; Batista, CD; Zapf, VS; Jaime, M; Hansen, BR; Niedermayer, C; Rule, KC; Habicht, K; Prokes, K; Kiefer, K; Ressouche, E; Paduan, A; Kenzelmann, MWe study the strongly anisotropic quasi-one-dimensional S = 1 quantum magnet NiCl2 center dot 4SC(NH2)(2) using elastic and inelastic neutron scattering. We demonstrate that a magnetic field splits the excited doublet state and drives the lower doublet state to zero energy at a critical field H-c1. For H-c1 < H < H-c2, where H-c2 indicates the transition to a fully magnetized state, three-dimensional magnetic order is established with the AF moment perpendicular to the magnetic field. We mapped the temperature/magnetic field phase diagram, and we find that the total ordered magnetic moment reaches m(tot) = 2.1 mu(B) at the field mu H-0 = 6 T and is thus close to the saturation value of the fully ordered moment. We study the magnetic spin dynamics in the fully magnetized state for H > H-c2, and we demonstrate the presence of an AF interaction between Ni2+ on the two interpenetrating sublattices. In the antiferromagnetically ordered phase, the spin-waves that develop from the lower-energy doublet are split into two modes. This is most likely the result of the presence of the AF interaction between the interpenetrating lattices.© 2013 IOP Publishing LTD.