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Magnetic Order and Fluctuations in the Presence of Quenched Disorder in the Kagome Staircase System (Co1-xMgx)3V2O8



K. Fritsch, Zahra Yamani, S. Chang, Yiming Qiu, John R. Copley, M. Ramazanoglu, H. A. Dabkowska, B. D. Gaulin


Co3V2O8 is an orthorhombic magnet in which S=3/2} magnetic moments reside on two crystallographically inequivalent Co2+ sites, which decorate a stacked, buckled version of the two dimensional kagome lattice, the stacked kagome staircase. The magnetic interactions between the Co2+ moments in this structure lead to a complex magnetic phase diagram at low temperature, wherein it exhibits a series of five transitions below 11 K that ultimately culminate in a simple ferromagnetic ground state below Tapprox.}6.2 K. Here we report magnetization measurements on single and polycrystalline samples of (Co1-xMgx)3V2O8 for xless than}0.23. as well as elastic and inelastic neutron scattering measurements on single crystals of magnetically dilute (Co1-xMgx)3V2O8 for x=0.029 and x=0.194, in which non-magnetic Mg2+ ions substitute for magnetic Co2+. We find that a dilution of 2.9% leads to a suppression of the ferromagnetic transition temperature by approx.} 15% while a dilution level of 19.4% is sufficient to destroy ferromagnetic long-range order in this material down to a temperature of at least 1.5 K. The magnetic excitation spectrum is characterized by two spin-wave branches in the ordered phase for (Co1-xMgx)3V2O8 (x=0.029), similar to that of the pure x=0 material, and by broad diffuse scattering at temperatures below 10 K in (Co1-xMgx)3V2O8 (x=0.194). Such a strong dependence of the transition temperatures to long range order in the presence of quenched non-magnetic impurities is consistent with two-dimensional physics driving the transitions. We further provide a simple percolation model that semi-quantitatively explains the inability of this system to establish long-range magnetic order at the unusually-low dilution levels which we observe in our experiments.
Physical Review B


kagome lattice, percolation model, magnetic order


Fritsch, K. , Yamani, Z. , Chang, S. , Qiu, Y. , Copley, J. , Ramazanoglu, M. , Dabkowska, H. and Gaulin, B. (2012), Magnetic Order and Fluctuations in the Presence of Quenched Disorder in the Kagome Staircase System (Co<sub>1-x</sub>Mg<sub>x</sub>)<sub>3</sub>V<sub>2</sub>O<sub>8</sub>, Physical Review B, [online], (Accessed June 19, 2024)


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Created November 20, 2012, Updated October 12, 2021