Tuning magnetic frustration on the diamond lattice of the A-site magnetic spinels CoAl${}_{2-x}$Ga${}_x$O${}_4$: Lattice expansion and site disorder

Abstract

The spinels CoB${}_2$O${}_4$ with magnetic Co${}^{2+}$ ions on the diamond lattice A site can be frustrated because of competing near-neighbor ($J_1$) and next-near neighbor ($J_2$) interactions. Here we describe attempts to tune the relative strengths of these interactions by substitution on the non-magnetic B-site. The system we employ is CoAl${}_{2-x}$Ga${}_x$O${}_4$, where Al is systematically replaced by the larger Ga, ostensibly on the B site. As expected, Ga substitution expands the lattice, resulting in Co atoms on the A-site being pushed further from one other and thereby weakening magnetic interactions. In addition, Ga distributes between the B and the A site in a concentration dependent manner displacing an increasing amount of Co from the A site with increasing $x$. This increased inversion, which is confirmed by neutron diffraction studies carried out at room temperature, affects magnetic ordering very significantly, and changes the nature of the ground state. Modeling of the magnetic coupling illustrates the complexity that arises from the cation site disorder.

9 pages, 10 figures

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Cited by in corpus (5)

• Linear magnetoelectric effect as a signature of long-range collinear antiferromagnetic ordering in the frustrated spinel CoAl2O4
• Structural ground states of ($A,A^{\prime }$)Cr${}_2$O${}_4$($A$=Mg, Zn; $A^{\prime }$ = Co, Cu) spinel solid solutions: Spin-Jahn-Teller and Jahn-Teller effects
• Cluster glass transition and relaxation in random spinel CoGa2O4
• Dynamic Spin Fluctuations in the Frustrated A-site Spinel CuAl2O4
• Evolution of Magnetic and Orbital Properties in the Magnetically-Diluted A-Site Spinel Cu${}_{1-x}$Zn${}_x$Rh${}_2$O${}_4$