Abstract
A phase transition from metallic AFM-b antiferromagnetic state to Mott insulating G-type antiferromagnetic (G-AFM) state was found in Ca3(Ru1−xTix)2O7 at about x = 0.03 in our previous work. In the present, we focused on the study of the magnetic transition near the critical composition through detailed magnetization measurements. There is no intermediate magnetic phases between the AFM-b and G-AFM states, which is in contrasted to manganites where a similar magnetic phase transition takes place through the presence of several intermediate magnetic phases. The AFM-b-to-G-AFM transition in Ca3(Ru1−xTix)2O7 happens through a phase separation process in the 2–5% Ti range, whereas similar magnetic transitions in manganites are tuned by 50–70% chemical substitutions. We discussed the possible origin of such an unusual magnetic transition and compared with that in manganites.
Highlights
We focus on the issue: how does a metallic AFM-b state evolve to an insulating G-AFM state? In manganites, a similar magnetic transition takes place through several intermediate distinct magnetic phase, such as A-AFM (i.e. FM layers coupled antiferromagnetically), C-AFM (i.e. FM rods coupled antiferromagnetically), CE-AFM (i.e. Zigzag FM chains coupled antiferromagnetically)[34,35,36,37]
Unlike our previously-reported phase diagram[28] which shows the evolution of magnetic structure in a wide composition range, the current phase diagram is focused on the magnetic phase separation region near the critical Ti concentration
Our goal of establishing such a detailed phase diagram is to examine if there exists any other intermediate magnetic phases between the AFM-b and G-AFM phase
Summary
When Ti doping level is increased to 4%, at 2 K, we still observe a trace of the metamagnetic transition arising from the polarization of AFM-b phase when the field is applied along the b-axis (Fig. 4c, inset) This feature indicates a negligible amount of AFM-b phase at the ground state of the 4% Ti doped sample. These results, together with the observation of the evolution of AFM-a phase with temperature and Ti concentration, demonstrate that in Ca3Ru2O7, the double exchange FM interaction and AFM superexchange interaction between Ru ions have comparable energy scales This makes the magnetic ground state of Ca3Ru2O7 extremely sensitive to impurity scattering such that a few percent Ti impurity doping can trigger a transition between two distinct magnetic ordered states, i.e. from AFM-b to G-AFM
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