Metamagnetism and soliton excitations in the modulated ferromagnetic Ising chain CoV₂O₆

TY - JOUR

T1 - Metamagnetism and soliton excitations in the modulated ferromagnetic Ising chain CoV2O6

AU - Kimber, S.A.

AU - Mutka, H.

AU - Chatterji, T.

AU - Hofmann, T.

AU - Henry, P.F.

AU - Bordallo, Heloisa N.

AU - Argyriou, D.N.

AU - Attfield, P.

PY - 2011/9/15

Y1 - 2011/9/15

N2 - We report a combination of physical property and neutron scattering measurements for polycrystalline samples of the one-dimensional spin-chain compound CoV2O6. Heat capacity measurements show that an effective S=1/2 state is found at low temperatures and that magnetic fluctuations persist up to ∼6TN. Above TN=6.3 K, measurements of the magnetic susceptibility as a function of T and H show that the nearest-neighbor exchange is ferromagnetic. In the ordered state, we have discovered a crossover from a metamagnet with strong fluctuations between 5 K and TN to a state with a 1/3 magnetization plateau at 2<T<5 K. We use neutron powder diffraction measurements to show that the antiferromagnetic state has incommensurate long-range order and inelastic time-of-flight neutron scattering to examine the magnetic fluctuations as a function of temperature. Above TN, we find two broad bands between 3.5 and 5 meV and thermally activated low-energy features which correspond to transitions within these bands. These features show that the excitations are deconfined solitons rather than the static spin reversals predicted for a uniform ferromagnetic Ising spin chain. Below TN, we find a ladder of states due to the confining effect of the internal field. A region of weak confinement below TN, but above 5 K, is identified which may correspond to a crossover between two- and three-dimensional magnetic ordering.

AB - We report a combination of physical property and neutron scattering measurements for polycrystalline samples of the one-dimensional spin-chain compound CoV2O6. Heat capacity measurements show that an effective S=1/2 state is found at low temperatures and that magnetic fluctuations persist up to ∼6TN. Above TN=6.3 K, measurements of the magnetic susceptibility as a function of T and H show that the nearest-neighbor exchange is ferromagnetic. In the ordered state, we have discovered a crossover from a metamagnet with strong fluctuations between 5 K and TN to a state with a 1/3 magnetization plateau at 2<T<5 K. We use neutron powder diffraction measurements to show that the antiferromagnetic state has incommensurate long-range order and inelastic time-of-flight neutron scattering to examine the magnetic fluctuations as a function of temperature. Above TN, we find two broad bands between 3.5 and 5 meV and thermally activated low-energy features which correspond to transitions within these bands. These features show that the excitations are deconfined solitons rather than the static spin reversals predicted for a uniform ferromagnetic Ising spin chain. Below TN, we find a ladder of states due to the confining effect of the internal field. A region of weak confinement below TN, but above 5 K, is identified which may correspond to a crossover between two- and three-dimensional magnetic ordering.

U2 - 10.1103/PhysRevB.84.104425

DO - 10.1103/PhysRevB.84.104425

M3 - Journal article

SN - 2469-9950

VL - 84

SP - 104425

JO - Physical Review B

JF - Physical Review B

IS - 10

ER -