Tuning of the spin gap transition of spin dimer compoundBa3Mn2O8 by doping with La and V

Abstract

We have successfully synthesized the coupled spin dimer systemsLaxBa3−xMn2O8 (x = 0, 0.2, 0.5,1) and Ba3Mn2−yVyO8 (y = 0.5, 1.0, 2.0). The magnetic properties have been investigated as a function ofmagnetic field and temperature down to 2 K. The susceptibility increases and theintradimer spin exchange interaction decreases with increase of La concentration.The most important finding in higher La doped systems reveals hysteresisin magnetization as a function of magnetic field. The substitution of La (x = 0.5, 1.0) for Ba induces ferromagnetism due to the formation of a mixed valencestate of Mn and enhancement of the inter-bilayer ferromagnetic interaction. Thereplacement of Mn by non-magnetic V destroys the spin gap. La and V dopingsignificantly affect the magnetic properties of the quantum antiferromagnetic compoundBa3Mn2O8.