The study of nearest- and next-nearest-neighbour magnetic interactions in seven tetragonal compounds of V(IV) containing linear chains and square lattices

Abstract

A new crystal chemical method was used to calculate the sign and strength not only of the nearest-neighbor (NN) interactions, but also of the next-nearestneighbor (NNN) ones in tetragonal compounds Zn 2 (VO)(PO 4 ) 2 (I), (VO)(H 2 PO 4 ) 2 (II), (VO)SiP 2 O 8 (III), (VO)SO 4 (IV), (VO)MoO 4 (V), Li 2 (VO)SiO 4 (VI) and Li 2 (VO)GeO 4 (VII) with similar sublattices of V 4+ ions on the basis of the room-temperature structural data. The reason for difference between respective magnetic interactions characteristics of these compounds was established. It is shown that the characteristic feature of these compounds is a strong dependence of the strength of magnetic interactions and the magnetic moments ordering type on slight displacements of XO 4 (X = P, Mo, Si or Ge) groups even without change of the crystal symmetry. In addition to extensively studied square lattice, other specific geometrical configurations of V 4+ were discovered. These configurations can result in frustration of magnetic interactions, namely linear chains along the c-axis with competing nearest-and next-to-nearest-neighbor interactions; rectangular (in I) and triangular (in II-VII) lattices with non-equivalent nearest-to-neighbor interactions, which can be also considered as n-leg ladders; one extra square lattice in the ab-plane with longer range interactions. It was concluded that virtually all magnetic interactions in these compounds were frustrated.Our estimation of magnetic interactions shows that in all compounds I-VII the antiferromagnetic nearest-neighbor J 1 interactions in linear chains along the c-axis are at least six times stronger than other J 2 -J 8 interactions. However, these interactions compete with weaker J 7 ( s s J J 1 7 ≅ 1/6) AF next-13 nearest-neighbor interactions in a chain. For nearest-and next-nearest-neighbor interactions in antiferromagnetic chain, instability against spontaneous dimerization for NN c NNN NNN J J J 6 1 ≅ > wasfound [21]. One can assume that, in addition to the competition between J 1 and J 7 interactions in chains along the c-axis, a competition between other interactions in these systems takes place. Let us consider the competition between interactions on the basis of representation of the structure of these compounds as crossed diagonal planes of a unit cell. As shown above, these planes comprise rectangular lattices with two non-equivalent nearest-neighbor bonds (J 1 ≠J 2 ) in Zn 2 (VO)(PO 4 ) 2 and distorted triangular lattices with three non-equivalent nearest-neighbor bonds (J 1 ≠J 2 ≠J 3 ) in other compounds (figure 2). Determination of competition between interactions J 1 , J 2 and J 3 in rectangulars and triangles, which are basic elements of these lattices, is of great difficulty because of non-equivalence of strengths of interactions and superposition of competitions by additional next-nearest-neighbor interactions. Based only on the signs of interactions, which we calculated, the rectangles with FM J 3 interactions (along diagonals) and AF J 1 and FM J 2 interactions (along the sides) (J ...

Search of low-dimensional magnetics on the basis of structural data: spin-1/2 antiferromagnetic zigzag chain compounds In2VO5, β-Sr(VOAsO4)2, (NH4,K)2VOF4and α-ZnV3O8

“…As a result, it was found that the majority of the 40 selected compounds are lowdimensional magnetics. A detailed analysis of magnetic couplings and geometrical frustrations in seven of these compounds -(Zn 2 (VO)(PO 4 ), (VO)(H 2 PO 4 ) 2 , (VO)SiP 2 O 8 , (VO)SO 4 , (VO)MoO 4 , Li 2 (VO)SiO 4 and Li 2 (VO)GeO 4 ) -containing spin-1/2 linear chains and square lattices was presented in [11]. Magnetic properties of three of the compounds -(VO)(H 2 PO 4 ) 2 , (VO)SiP 2 O 8 and Table . Parameters of main intra-and intеrchain couplings calculated on the basis of the structural data.…”

“…), (VO)(H 2 PO 4 ) 2 , (VO)SiP 2 O 8 , (VO)SO 4 , (VO)MoO 4 , Li 2 (VO)SiO4 and Li 2 (VO)GeO 4 ) -containing spin-1/2 linear chains and square lattices was presented in[11]. Magnetic properties of three of the compounds -(VO)(H 2 PO 4 ) 2 , (VO)SiP 2 O 8 andTable.Parameters of main intra-and intеrchain couplings calculated on the basis of the structural data.…”

Bicritical Central Point of Ising Model Phase Diagram

“…The study of frustrated magnetic systems always arouses the interest [1][2][3][4][5][6][7]. It is known that the nature of the ordering at low temperatures regime of these materials depends on the concentration of the magnetic species and on the relative magnitude of competing energy scales [8,9].…”