Direct Imaging of Dynamic Glassy Behavior in a Strained Manganite Film

Abstract

Complex many-body interaction in perovskite manganites gives rise to a strong competition between ferromagnetic metallic and charge ordered phases with nanoscale electronic inhomogeneity and glassy behaviors. Investigating this glassy state requires high resolution imaging techniques with sufficient sensitivity and stability. Here, we present the results of a near-field microwave microscope imaging on the strain driven glassy state in a manganite film. The high contrast between the two electrically distinct phases allows direct visualization of the phase separation. The low temperature microscopic configurations differ upon cooling with different thermal histories. At sufficiently high temperatures, we observe switching between the two phases in either direction. The dynamic switching, however, stops below the glass transition temperature. Compared with the magnetization data, the phase separation was microscopically frozen, while spin relaxation was found in a short period of time.

Optically coupled methods for microwave impedance microscopy

“…MIM has been applied successfully to measure conductivity inhomogeneity in a wide variety of systems, including carbon nano-tubes [3], graphene [4], In 2 Se 3 nanoribbons [5], quantum hall edge states [6], MoS 2 field effect transistors [7], and more [8][9][10][11][12][13][14][15][16][17][18].…”

Misfit Relaxation Mechanisms and Domain Ordering in Anisotropically Strained Manganite Thin Films

“…The MFM morphology of the red box region (Figure 5j,k) displays regular and ordered FMM structural domains, but its distribution (Figure 5k) is different from that in Figure S5h of the same region, indicating the nonergodicity. 45 Again, these domain stripes form ∼71 or 109°domains, as shown in Figure 5k. As the magnetic field decreases, the FMM domains annihilate gradually, implying that the COO phase recovers partially (Figure 5l,m).…”

Gate Control of Percolative Conduction in Strongly Correlated Manganite Films

“…Although these estimates are dependent on details of individual models, the percolation threshold in two‐dimensional systems is always higher than that in three‐dimensional systems . Additionally, a recent report on real‐space domain observations in Pr 0.55 (Ca 0.75 Sr 0.25 ) 0.45 MnO 3 thin films using a microwave impedance microscope suggests that the typical domain size is 500 nm to 1 μm, which is larger than the film thickness used here . Thus the most likely model which can explain the present MIT is a quasi‐two dimensional percolation transition.…”

“…A possible scenario for this field effect is that the first order transition induced by the stimuli at the surface is collectively expanded to the whole film. Taking the known domain size of 500 nm ∼1 μm into account, the creation of a domain wall between insulating and metallic states in parallel to the surface in films thinner than the 500 nm costs too much domain wall energy. Therefore, the connection of the domains is modulated in the entire film even for a thickness of 50 nm.…”