title: Successive orbital ordering transitions in NaVO2.
abstract: Physical property measurements on samples of triangular-lattice NaVO2 reveal two successive orbital ordering transitions. At 300 K, the structure is rhombohedral. At 98 K, the system undergoes a second-order transition to a monoclinic phase in which the in-plane V-V distances separate into four short and two long bonds, corresponding to orbital ordering of one electron per V3+. Below 93 K, there is a first-order transition to a second monoclinic phase with four long and two short V-V bonds, consistent with orbital ordering of two electrons per V3+. Long range magnetic ordering of 0.98(2)mu_(B) per V3+ (3d(2)) sets in at the 93 K structural transition. The orbital ordering relieves the geometric frustration and leads to a magnetically ordered ground state.
authors.affiliation: Department of Chemistry, Princeton University, Princeton, NJ 08544, USA.
authors.forename: T M
authors.initials: TM
authors.lastname: McQueen
authors.forename: P W
authors.initials: PW
authors.lastname: Stephens
authors.forename: Q
authors.initials: Q
authors.lastname: Huang
authors.forename: T
authors.initials: T
authors.lastname: Klimczuk
authors.forename: F
authors.initials: F
authors.lastname: Ronning
authors.forename: R J
authors.initials: RJ
authors.lastname: Cava