Abstract:
Complex metal oxides are a curious class of materials with diverse states of matter, such as magnetism, superconductivity, multiferroics, topological phases, and many more. One of the exciting features of these materials is the coupling of orbital, lattice, spin, and charge degrees of freedom. Specifically, in heavy materials like 5d Iridates, the spin and orbit components are mixed, yielding pseudospins and giving rise to effects like pseudospin lattice coupling, which connects lattice distortion in the system with pseudospins. In the bigger picture, such effects can be attributed to magnetoelastic couplings, and we probe the lattice by applying strain to the system to study its effect on magnetic ordering. We implemented a uniaxial strain application using strain cells in bulk materials. When an in-situ uniaxial strain of B2g symmetry is applied to single crystal Sr2IrO4, we observed a “new state” below the Néel Temperature (TN) that breaks the translational symmetry of a crystal lattice, evidenced by the observation of (1 0 L = 2n ± 1/3) satellite peaks in the X-ray resonance magnetic scattering measurements and an unusual long-extended tail in the Magnetoresistance. We investigated the minimal free energy model of the metamagnetic transition to identify the fundamental interactions responsible for this new state. The proposed model simulates the B2g strain effect and the emergent state very well by including a nontrivial quartic interaction of two-fold rotational symmetry that is in-situ tuned by strain and different from the rotation invariant quartic interactions. In addition, we observed a strain-induced highly tunable incommensurate (IC) magnetic order just below the TN, with no spontaneous incommensurate instability. By applying strains of different symmetry channels and signs, i.e., tensile and compressive, we unveiled that the IC order is induced when the strain-induced anisotropy competes against the spontaneous anisotropy in an orthogonal symmetry channel.