Magnetic frustration, spirals and short-range order in Cr_xFe_{1 –x}VO₄–I solid solutions

Abstract

The crystal and magnetic structures of Cr,Fe,-,VO,-l solid solutions with x=0.25, 0.50, and 0.75 have been investigated by neutron diffraction and magnetic susceptibility measurements. Site occupancy refinements and geometrical arguments show that there is a small degree of Cr3+/Fe3+ ordering between two inequivalent octahedral sites with increasing x, as Cr3+ preferentially occupies the site that can become more regular. Antiferromagnetic order is observed below the N6el temperature TN=21.8(5) and 17.9(2) K for the x=O.25 and 0.50 samples, respectively, and can be described by the propagation vector (0, z,, 5) where z,=O.161(3) for x= 0.25 and z, = 0.25(1) for x= 0.50. The magnetic structures contain clusters of four antiferromagnetically coupled spins, but the order between clusters is frustrated, resulting in magnetic spirals that propagate along the monoclinic b axis. The frustration also gives rise to increasing amounts of short-range magnetic order with increasing x, such that no long-range order is observed for x=O.75.

Stability of FeVO4 under Pressure: An X-ray Diffraction and First-Principles Study

“…Earlier studies on FeVO 4 have often indicated the formation of CrVO 4 -type or α-MnMoO 4 -type in low-temperature synthesis, whereas wolframite or α-PbO 2 -type phases appear at high-temperature synthesis (Figure ). On the other hand, the transition from FeVO 4 - I to CrVO 4 -type orthorhombic phase (FeVO 4 - II ) on substitution of amounts (about 20%) of Cr 3+ in the FeVO 4 - I lattice was observed. , The authors have indicated a small decrease in the unit cell volume (≈1.7%) can transform the triclinic FeVO 4 to monoclinic α-MnMoO 4 -type (SG C 2/ m ) structure. However, similar solid solutions at lower concentration (<20%) retain the original triclinic structure of FeVO 4 - I . ,, …”

“…There is an important list of AB O 4 compounds that crystallize in this structure, being the most representative the A WO 4 compounds. − The crystal structure of the FeVO 4 polymorphs is shown in Figure . Besides, the structural changes in FeVO 4 by chemical substitution have also been investigated in order to understand its structural variation as well as to tune its physical and chemical properties. ,,, It has been observed that a small substitution of other cations transforms the triclinic FeVO 4 - I to the monoclinic (SG C 2/ m ) α-MnMoO 4 -type structure and it remains stable in a wider range of compositions.…”

“…Besides, the structural changes in FeVO 4 by chemical substitution have also been investigated in order to understand its structural variation as well as to tune its physical and chemical properties. 21,23,42,43 It has been observed that a small substitution of other cations transforms the triclinic FeVO 4 -I to the monoclinic (SG C2/m) α-MnMoO 4 -type structure and it remains stable in a wider range of compositions.…”

Synthesis and properties of Fe0.83V1.17O4

“…Phase X crystallizes in the monoclinic system and its endcentered (C) unit cell parameters are given in Table 4. The literature scan has shown that angular positions of diffraction reflection, their relative intensities and unit cell parameter of phase X are similar to these ones of Fe 1-x Cr x VO 4 solid solution phase, CrVO 4 -I and InVO 4 -I, which are isostructural with a-MnMoO 4 [13][14][15][16]. It permits advancing suggestion, that phase X belongs to a group of orthovanadates, MVO 4 , isostructural with a-MnMoO 4 .…”

“…The literature survey has shown as well that in the FeVO 4 -CrVO 4 system solid solution of general formula Fe 1-x Cr x VO 4, for 0.1 \ x \ 0.85, forms, which adopts aMnMoO 4 structure [13,14]. Thus, the structure of the Fe 1-x Cr x VO 4 phase differs essentially from the stable at ambient conditions structures of triclinic FeVO 4 -I and orthorhombic CrVO 4 -III.…”