Commensurate to incommensurate magnetic phase transition in Honeycomb-lattice pyrovanadate Mn2V2O7

Abstract

We have synthesized single crystalline sample of Mn${}_2$V${}_2$O${}_7$ using floating zone technique and investigated the ground state using magnetic susceptibility, heat capacity and neutron diffraction. Our magnetic susceptibility and heat capacity reveal two successive magnetic transitions at $T_{N1}=$ 19 K and $T_{N2}=$ 11.8 K indicating two distinct magnetically ordered phases. The single crystal neutron diffraction study shows that in the temperature ($T$) range 11.8 K $\le T\le$ 19 K the magnetic structure is commensurate with propagation vector $k_1=(0,0.5,0)$, while upon lowering temperature below $T_{N2}=$ 11.8 K an incommensurate magnetic order emerges with $k_2=(0.38,0.48,0.5)$ and the magnetic structure can be represented by cycloidal modulation of the Mn spin in $ac-$plane. We are reporting this commensurate to incommensurate transition for the first time. We discuss the role of the magnetic exchange interactions and spin-orbital coupling on the stability of the observed magnetic phase transitions.

8 pages, 7 figures