Field-induced partial order in the spin ice dysprosium titanate

Abstract

Neutron scattering has been used to investigate the magnetic correlations in the the spin ice material dysprosium titanate, Dy 2 Ti 2 O 7 . An isotopically enriched sample was used to minimise neutron absorption. In zero field no magnetic order was observed down to 50 mK but the magnetic diffuse scattering was in qualitative agreement with that expected for the disordered low temperature state of dipolar spin ice. Application of a field of ≈ 0.8T in the [100] direction led to long range order. With the field applied in the [110] direction a coexistence of long range ferromagnetic and short range antiferromagnetic order was observed. This is attributed to the pinning of only half the spins by the field. The hysteresis loops in both field orientations displayed unusual steps and plateaus. 75.25.+z,75.40.Gb,75.50.Lk

Spin Ice

“…[57,107,122] and the bulk measurements of Ref. [120] are in reasonable agreement regarding the general features of the phase diagram shown in Figure 7.28.…”

A lattice dynamical investigation of the Raman and the infrared frequencies of the Dy2Ti2O7 pyrochlore spin ice compound

“…Recently, it has been observed that the cubic pyrochlore Dy 2 Ti 2 O 7 demonstrates the spin ice state and the coexistence of long range ferromagnetic and short range antiferromagnetic order in a magnetic field applied along the [1 1 0] axis [1,2]. For the information on phonons, charge carriers and spins, this geometrically frustrated pyrochlore Dy 2 Ti 2 O 7 (space group O h 7 ) had been studied experimentally for its infrared and Raman modes [3][4][5][6].…”

Monte Carlo studies of the dipolar spin ice model

“…A number of recent experiments 60,61,62,64,80 have shown a rich variety of new behavior when spin ice materials are subjected to such a field, which warrants some theoretical investigation.…”

“…They suggested that this behavior would arise from long-range ferromagnetic order occurring in field-coupled spin chains (called α chains by Hiroi 62 ), and short-range "antiferromagnetic" order occurring in the field-decoupled spin chains (β chains). 80 In this argument, the true ground state is a q = X structure that is dynamically inhibited from being accessed on experimental timescales.…”

“…This suggests that this ordered state should be one of the ground states for the interacting dipolar spin ice model, with a sufficiently strong external field h//[100]. Indeed, this order has been observed experimentally 80 on samples of Dy 2 Ti 2 O 7 . For h//[110], only two of the four spins on a tetrahedron couple to the field.…”