Evolution of spin correlations in SrDy2O4 in an applied magnetic field

Abstract

The development of short-and long-range magnetic order induced in a frustrated zigzag ladder compound SrDy 2 O 4 by an applied field is studied using neutron-diffraction techniques. In zero field, SrDy 2 O 4 lacks long-range magnetic order down to temperatures as low as 60 mK, and the observed powder-neutron-diffraction (PND) patterns are dominated by very broad diffuse scattering peaks. Single-crystal neutron diffraction reveals that the zero-field magnetic structure consists of a collection of antiferromagnetic chains running along the c axis and that there is very little correlation between the chains in the ab plane. In an applied magnetic field, the broad diffuse scattering features in PND are gradually replaced by much sharper peaks, however, the pattern remains rather complex, reflecting the highly anisotropic nature of SrDy 2 O 4 . Single-crystal neutron diffraction shows that a moderate field applied along the b axis induces an up-up-down magnetic order associated with a 1 3 -magnetization plateau, in which magnetic correlation length in the ab plane is significantly increased, but it nevertheless remains finite. The resolution-limited k = 0 peaks associated with a ferromagnetic arrangement appear in powder and single-crystal neutron-diffraction patterns in fields of 2.5 T and above.

Field-Induced Transitions in Highly Frustrated SrHo2O4

“…Finally, it is interesting to compare the diffraction patterns of the field dependence of the scattering from SrHo 2 O 4 for H b (along which a plateau in magnetisation is stabilised) to those observed in SrDy 2 O 4 [7]. In both compounds, the initially broad diffuse scattering features seen in zero field are significantly enhanced and sharpened by the applied field.…”

“…Therefore, the second type of short-range order present in this material is one-dimensional in real space, and it persists over a wider temperature range-the onset of these correlations may also be observed with bulk heat capacity measurements as the broad peak around ∼3 K. The coexistence of the two types of diffuse scattering in SrHo 2 O 4 is likely to be the result of the presence of two crystallographically inequivalent sites for Ho 3+ in the unit cell. Other members of the SrLn 2 O 4 series, SrEr 2 O 4 and SrDy 2 O 4 , also show the coexistence of two markedly different types of magnetic ordering at low-temperatures [7,15,16].…”

“…The inequivalent sites of the lanthanides are shown in red and blue. Single crystals of the oxides have been grown [3], and several SrLn 2 O 4 compounds, where Ln = Er [4,5], Dy [6,7], Gd [8] and Yb [9,10], have been studied in detail. All the crystals are magnetically highly anisotropic-for example, the electronic structure of Ho 3+ coupled with the crystalline electric field (CEF) allows it to display Ising like properties at low temperature, and the presence of low-lying CEF levels manifests as a large anisotropy in the Curie-Weiss temperatures for the three principal crystal directions of SrHo 2 O 4 (θ CW is negative for a field applied along the a-axis and positive for a field along b-axis) [5].…”

Enhancement of magnetization plateaus in low-dimensional spin systems

“…The frustrated chain (α = 0) at a uniform field is known to exhibit a magnetization plateau at m = 1/3 due to an even less relevant umklapp operator [18,29,86]. However, when the site modulation dependence of the g factor is switched on, the periodicity of the model changes, now G = π 2a , and the more relevant operator O π/2 2 will be present and easily prevail.…”

Magnetic structure and low-temperature properties of geometrically frustrated SrNd2O4

“…This geometry, combined with the antiferromagnetic exchange interactions, results in a behavior typically associated with geometrical frustration, such as suppression of the magnetic ordering down to very low temperatures, complex and fragile ground states sensitive to minute perturbations, as well as the appearance of magnetization plateaus in an applied field. Previous studies of the SrLn 2 O 4 family mostly focused on the heavy rareearth members, such as SrGd 2 O 4 [2][3][4], SrDy 2 O 4 [5][6][7][8][9][10], SrHo 2 O 4 [11][12][13][14][15], SrEr 2 O 4 [13,[16][17][18][19][20], and SrYb 2 O 4 [21]. The magnetic properties of SrNd 2 O 4 containing a lighter lanthanide, Nd, have not yet been reported, although BaNd 2 O 4 and BaTb 2 O 4 have been investigated with magnetization, heat capacity, and powder neutron diffraction measurements [22,23].…”