Fragile ground state and rigid field-induced structures in the zigzag ladder compound BaDy2O4

Abstract

We report on a sequence of field-induced transitions in the zigzag ladder compound BaDy2O4 studied with powder neutron diffraction and magnetisation measurements. In agreement with the previously published results, the low temperature zero-field structure is characterised by two half-integer propagation vectors, k1 = [ 1 2 0 1 2 ] and k2 = [ 1 2 1 2 1 2 ]. However, on application of an external magnetic field, the Bragg peaks corresponding to the zero-field structure lose their intensity rather rapidly and disappear completely in a field of 2.5 kOe. In the intermediate fields, 2.5 to 22.5 kOe, new peaks are observed characterised by the propagation vector k = [0 0 1 3 ] corresponding to an up-up-down (uud) structure as well k = 0 ferromagnetic peaks. This regime of fields corresponds to a pronounced plateau in the magnetisation curve. Remarkably, the uud structure survives heating to at least 1.4 K, three times higher temperature than the TN of 0.48 K for the zero-field structure. Above 22.5 kOe, the k peaks disappear while the k = 0 peaks gain significant intensity indicating an increase in the polarisation of the system. The analysis of the intensities of the field-induced reflections allows for a clear identification of the magnetic structures in both the intermediate and high field regimes.

Field-induced magnetic states in geometrically frustrated SrEr2O4

“…From a neutron diffraction perspective, such a UUD structure can be decomposed into a sinusoidally modulated component with a propagation vector q = (0 0 1 /3) and a ferromagnetic component. For equally sized moments, the ferromagnetic component needs to be exactly 1 /4 of the antiferromagnetic amplitude, although there is no general requirement for such a restriction and a UUD structure with variable size moments have been found, for example, in BaDy 2 O 4 [31].…”

Quantum magnetism of ferromagnetic spin dimers in $α$-KVOPO$_4$

“…Figure 11(a) represents the Rietveld refinement of the nuclear pattern at T = 10 K using the orthorhombic crystal structure with the space group P na2 1 [51] ment with the refined values from the powder XRD data at room temperature [18]. Magnetic structure refinement was performed for the diffraction data from the paired 2 and 9 detector banks of the diffractometer because of the best resolution (at an average 2θ value of 58.308 • ) [52]. Figure 11(b) shows the combined Rietveld refinement of the nuclear and magnetic reflections at T = 1.5 K. A solution was found in the magnetic space group P 1.…”

An Ising model on a 3D honeycomb zigzag-ladder lattice: a solution to the ground-state problem and application to the SrRE$_2$O$_4$ and BaRE$_2$O$_4$ magnets

“…The two magnetic sites have their magnetization easy-axes aligned along (or very near) the two crystallographic axes, while when the field is applied along the third crystallographic axis, the measured magnetization is significantly lower (particularly for Ho and Er compounds [7]) suggesting that it is a hard magnetization axis for both sites. Apart from the magnetization data, the evidence for the field-induced uud structure comes from the results of neutron diffraction for SrDy 2 O 4 [12,13], SrHo 2 O 4 [14], SrEr 2 O 4 [37] and BaDy 2 O 4 [15]. The uud structures are characterized by the appearance of the sharp, almost resolution-limited magnetic peaks at non-integer positions.…”

“…. In an applied field, the uud structure is inferred from powder neutron diffraction measurements and from a pronounced plateau in the magnetization curve [15]. The uud structure appears to be much more stable than the zero field states, but finding any further intermediate magnetic states in BaDy 2 O 4 will be experimentally challenging in the absence of a large size single crystal samples of this compound.…”

“…These are 3D honeycomb zigzag-ladder magnets such as SrRE 2 O 4 [1,2] and BaRE 2 O 4 [3][4][5][6], where RE is a rare earth atom. These families of compounds exhibit a very rich magnetic behavior, especially in an external magnetic field [7][8][9][10][11][12][13][14][15]. Rare earth magnetic atoms in these compounds occupy two crystallographically inequivalent positions with substantially different values of magnetic moments (which can be considered as classical ones) and, very often, almost orthogonal axes of easy magnetization.…”