Critical behavior in the inhomogeneous ferromagnetSrFe0.80Co0.20O3.

Abstract

A detailed muon spin relaxation (μSR) and magnetization study is presented of the paramagnetic-toferromagnetic transition in the compound SrFe 0.80 Co 0.20 O 3 . The critical exponents derived from the static critical analysis are close to the theoretical predictions for the Heisenberg model in three dimensions. However, a small drift toward mean-field values is interpreted as arising from the presence of long-range dipolar interactions between the Fe(IV) centers. The evolution of spin dynamics across the transition determined from the μSR study is consistent with this interpretation. μSR and magnetization data also provide evidence of an inhomogeneous magnetic state both above and below T c , placing this system in line with other double-exchange materials such as manganites and cobaltites where spontaneous electronic and magnetic phase separation appears conspicuous and explains much of the encountered experimental phenomenology.

Nature of novel criticality in ternary transition-metal oxides

“…That happens when the doping with another transition metal breaks the double-exchange bonds or the doping with another rare earth introduces a disorder in the magnitude of double exchange (see Table 1, rows 4–6). Incidentally, a small drift from the 3 d -Heisenberg toward the mean-field model in the inhomogeneous SrFe 0.80 Co 0.20 O 3.0 ferromagnet is supposed to arise from the presence of the dipolar interactions between the Fe 4+ cations 27 .…”

“…The lattice, Mott, magnetic and ferroelectric transitions inherent TTMO give diversity of their interdependence: the critical temperatures nonlinear and very-sensitive to magnetic and electric fields and pressure; hysteresis and so tricritical points; and, finally, novel criticality which is the culmination of the all. So, discovering the nature of the novel criticality is very important for understanding of amazing properties of TTMO in tailoring principal-new spintronic devices on the base of the film heterostructures 27–30 of the alternated layers of a TTMO with the ferroelectric, insulator, semiconductor, semimetal, or superconductor.…”

Evidence of ferromagnetic short-range correlations in cubic La1−xSrxMnO3−δ(x = 0.80, 0.85) above antiferromagnetic ordering

“…An experimental µ eff more than the theoretical µ eff corresponds to magnetic polarons with FM interaction and vice versa. Furthermore, the χ −1 ( T ) below T FMC shows a sharp down turn, which is considered to be the hallmark of stabilization of interacting FM polarons in a PM matrix and rejects the possibility of smeared phase transition , which will show an upturn in χ −1 ( T ) curves. The oxygen off‐stoichiometric samples show similar χ −1 ( T ) behavior as that of stoichiometric ones with only a few Kelvin shifts in T FMC accompanied by the weakening of AFM correlations.…”

“…An experimental µ eff more than the theoretical µ eff corresponds to magnetic polarons with FM interaction and vis a vis. Further the  -1 (T) below T FMC shows a sharp down turn, which is considered to be the hallmark of stabilization of interacting FM polarons in PM matrix [10][11][12]23,24 and rejects the possibility of smeared phase transition 39,40,41 which will show an upturn in  -1 (T)…”

Effect of ferromagnetic proximity on critical behavior

“…2 The critical exponents are known to vary with the magnetic interactions, anisotropy, and the extension of the sample. A large number of studies have still verified the validity of the scaling hypothesis [3][4][5][6][7][8] in crossover regions, where the spatial or spin dimensionality is in between two universality classes. [9][10][11][12][13][14] The two-dimensional (2D) XY class has a special significance in the history of critical phenomena.…”