Thermal expansion and specific heat of magnetically frustrated (Ni1-xCox)3V2O8

Ni3V2O8 and Co3V2O8 both have the same basic kagome-staircase structure, leading to geometric frustration of the magnetic ordering of the spins on Ni and Co sites. Both compounds exhibit a number of magnetic phase transitions at low temperatures, which partially relieve the frustration. In addition to magnetic ordering, these compounds also exhibit ferroelectric properties. Here we present thermal expansion and specific heat data on high-quality single crystals of (Ni1-xCox)3V2O8, which allow us to map out the phase diagram of the Ni-Co series, as well as to calculate various pressure derivatives associated with magnetic ordering. (orig.)