Uniaxial-Pressure Control of Magnetic Phase Transitions in a Frustrated Magnet CuFe1-xGaxO2 (x=0, 0.018)

We have investigated effects of applied uniaxial pressure ( p ) on magnetic phase transitions in a triangular lattice antiferromagnet CuFeO 2 (CFO) and a slightly Ga-substituted compound CuFe 1- x Ga x O 2 (CFGO) with x =0.018. We have performed neutron diffraction, spherical neutron polarimetry, magnetic susceptibility and pyroelectric measurements under p up to 100 MPa applied on the [1\bar10] surfaces of the single crystal samples. As a result, we have revealed that in both of CFO and CFGO ( x =0.018), the application of p significantly increases the transition temperature from the paramagnetic phase to a collinear incommensurate antiferromagnetic phase, at which these systems exhibit a crystal structural distortion associated with the magnetic ordering. This suggests that the application of p beaks equilateral symmetry of the triangular lattice above the original transition temperature, and partially relieves geometrical spin frustration, which generally suppresses long-range magnetic orderings even a...