Absence of long-range order in the frustrated magnet SrDy2O4 due to trapped defects from a dimensionality crossover

Abstract

Magnetic frustration and low dimensionality can prevent long range magnetic order and lead to exotic correlated ground states. SrDy 2 O 4 consists of magnetic Dy 3+ ions forming magnetically frustrated zig-zag chains along the c-axis and shows no long range order to temperatures as low as T = 60 mK. We carried out neutron scattering and AC magnetic susceptibility measurements using powder and single crystals of SrDy 2 O 4 . Diffuse neutron scattering indicates strong one-dimensional (1D) magnetic correlations along the chain direction that can be qualitatively accounted for by the axial next-nearest neighbour Ising (ANNNI) model with nearestneighbor and next-nearest-neighbor exchange J 1 = 0.3 meV and J 2 = 0.2 meV, respectively. Three-dimensional (3D) correlations become important below T * ≈ 0.7 K. At T = 60 mK, the short range correlations are characterized by a putative propagation vector k 1/2 = (0,2 ). We argue that the absence of long range order arises from the presence of slowly decaying 1D domain walls that are trapped due to 3D correlations. This stabilizes a low-temperature phase without long range magnetic order, but with well-ordered chain segments separated by slowly-moving domain walls.

Field dependence of the magnetic correlations of the frustrated magnetSrDy2O4

“…17 This is also the case for the field-induced magnetic structure presented here: the presence of a component along the a-axis does not improve significantly the χ 2 value and in that case its size is negligible compared to the component along the c-axis.…”

“…As discussed in our previous work, 17 the most likely interchain interactions are the dipolar interactions and the interaction J b , represented on Fig. 3(b), would be the dominant one.…”

“…A global scaling factor, a constant background and the χ 1 values were adjusted to obtain a reasonable description of the data. The susceptibilities were determined to be χ 17 The 1D ANNNI model predicts the presence of the ↑↑↓ state for longitudinal fields with antiferromagnetic J 1 and J 2 . [11][12][13] On the other hand, transverse fields should lead to quantum fluctuations and the ↑↑↓ state is not expected in that case.…”

“…Quantum fluctuations due to the transverse field should destabilize the order on site 1 but its presence suggests that, either the weak XY anisotropy of site 1 weakens this effect, or the applied field is not sufficient to reach the vicinity of the quantum critical point. However, the increase of quantum fluctuations appears to be sufficient to reduce to strength of the trapping mechanism, leading to the absence of long range order in zero field, 17 and help attain a long range field-induced phase in FC conditions.…”

“…6, 16 The presence of only short range correlations at the lowest temperatures in zero field has been justified by the trapping of slowly decaying defects due to a dimensionality crossover. 17 We report here a detailed characterization of the field-induced order by single crystal neutron diffraction. Our measurements reveal the presence of strong hysteretic effects and the existence of a three-dimensional (3D) long range order with a ↑↑↓ spin order along the chains.…”