Physical Review Letters ( IF 8.385 ) Pub Date :
D. Haskel, G. Fabbris, J. H. Kim, L. S. I. Veiga, J. R. L. Mardegan, C. A. Escanhoela Jr., S. Chikara, V. Struzhkin, T. Senthil, B. J. Kim, G. Cao, and J. W. Kim

The effect of compression on the magnetic ground state of Sr${}_{2}$IrO${}_{4}$ is studied with x-ray resonant techniques in the diamond anvil cell. The weak interlayer exchange coupling between square-planar 2D IrO${}_{2}$ layers is readily modified upon compression, with a crossover between magnetic structures around 7 GPa mimicking the effect of an applied magnetic field at ambient pressure. Higher pressures drive an order-disorder magnetic phase transition with no magnetic order detected above 17-20 GPa. The persistence of strong exchange interactions between ${J}_{eff}=1/2$ magnetic moments within the insulating IrO${}_{2}$ layers up to at least 35 GPa points to a highly frustrated magnetic state in compressed Sr${}_{2}$IrO${}_{4}$ opening the door for realization of novel quantum paramagnetic phases driven by extended $5d$ orbitals with entangled spin and orbital degrees of freedom.

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