Magnetic and thermal properties of theS=12zig-zag spin-chain compoundIn2

Yogesh Singh

¹

,

R. W. McCallum

²

,

D. C. Johnston

³

Abstract

Static magnetic susceptibility χ, ac susceptibility χac and specific heat C versus temperature T measurements on polycrystalline samples of In2VO5 and χ and C versus T measurements on the isostructural, nonmagnetic compound In2TiO5 are reported. A Curie-Wiess fit to the χ(T ) data above 175 K for In2VO5 indicates ferromagnetic exchange between V 4+ (S = 1/2) moments. Below 150 K the χ(T ) data deviate from the Curie-Weiss behavior but there is no signature of any long range magnetic order down to 1.8 K. There is a cusp at 2.8 K in the zero field cooled (ZFC) χ(T ) data measured in a magnetic field of 100 Oe and the ZFC and field cooled (FC) data show a bifurcation below this temperature. The frequency dependence of the χac(T ) data indicate that below 3 K the system is in a spin-glass state. The difference ∆C between the heat capacity of In2VO5 and In2TiO5 shows a broad anomaly peaked at 130 K. The entropy upto 300 K is more than what is expected for S = 1/2 moments. The anomaly in ∆C and the extra entropy suggests that there may be a structural change below 130 K in In2VO5.

The importance of the on-site electron–electron interaction for the magnetic coupling in the zigzag spin-chain compound In2VO5

“…Beyond, also the FM-AFM pattern shows a lower total energy than the FM-FM pattern. As a consequence, our GGA+U results reproduce the experimental situation that the magnetic exchange in In 2 VO 5 is predominantly AFM at low temperature [2][3][4].…”

“…In 2 VO 5 (space group Pnma) was first synthesized by Senegas et al [1] in 1975 who also obtained the lattice parameters at room temperature. Their lattice parameters have been confirmed by recent experiments [2][3][4]. From the magnetic point of view the compound is of special interest, because it gives rise to frustrated one-dimensional zigzag spin S = 1/2 chains.…”

“…Note that here and in the following energy values are given per V atom. As recent experimental studies [2][3][4] have indicated an interrelation between structural transitions and the crossover between the FM and AFM states at low temperature, we have optimized the experimental structure by minimizing the atomic forces to find the lowest energy crystal structure. The results are given in the right hand column of table 1.…”

“…Singh et al [3] have studied the magnetic and thermal properties of In 2 VO 5 in comparison to In 2 TiO 5 , which is an isostructural non-magnetic compound. They have measured the static magnetic susceptibility, the ac susceptibility, and the specific heat as functions of the temperature.…”