Reentrant spin glass behavior in polycrystalline La0.7Sr0.3Mn1-X FeX O 3

Abstract

The magnetic and transport properties of the compound La0.7Sr0.3Mn1-xFe xO 3 (0.1 < x <0.4) have been studied by means of electrical resistivity, AC magnetic susceptibility, and DC magnetization. At low concentrations (x <0.1), the system displays essentially para-to-ferromagnetic transitions as the temperature is decreased, although a decrease in the magnetic moment has been observed in previous studies at temperatures a little below T C. This ferromagnetism is explained by double exchange theory in terms of the formation of Mn+3/Mn+4 ions pairs in the system. At concentrations in the range 0.1 < x <0.4 the system is more complex. Increased Fe doping not only weakens the ferromagnetic (FM) order and augments the resistivity of the samples, but also induces the appearance of a reentrant spin glass phase at low temperatures (T < 60 K). Irreversibility of the magnetization measured with zero field cooling and with field cooling has been observed. In addition, the AC susceptibility peak position varies with frequency. All these effects are characteristic of spin glass behavior. The results have been interpreted based in an increase of frustration due to increasing competition between FM Mn+3/Mn+4 interactions and antiferromagnetic interactions between ions at the boundaries of Fe clusters

Magnetic order in perovskite-related SrFeO2F

“…Such re-entrant phases with random spin configurations are not uncommon in magnetic systems with some inbuilt disorder [9]. This has recently been exemplified in the perovskite-related oxide of composition La 0.7 Sr 0.3 Mn 1−x Fe x O 3 (0.1 < x < 0.4) in which the randomness arises from the competing magnetic interactions caused by the substitution by iron on the manganese site [10]. In SrFeO 2 F the randomness arises from the substitution by fluorine on the oxygen anion site causing different superexchange Fe 3+ -O 2− -Fe 3+ and Fe 3+ -F-Fe 3+ which, to give rise to disorder, would need to have contrasting values, for example be of different sign.…”

Magnetic properties of manganites doped with gallium, iron, and chromium ions

“…It was found that a long range ferromagnetic order appears in the LaMn 1 ⎯ x Ga x MnO 3 and LaMn 1 -x Sc x O 3 systems at x > 0. 15 in the absence of Mn 4+ ions [5][6][7][8]. A dielec tric ferromagnetic state was detected in [10][11][12].…”

“…The results obtained in [14][15][16][17][18][19][20] show that these substitutions gradually destroy a ferro magnetic state, which was interpreted in terms of weakening double exchange. According to [14][15][16][17][18][19][20], iron and chromium ions enter into a manganite lattice in the trivalent state despite the fact that they can be in the tetravalent state in perovskites. Gallium ions can only be in the trivalent state.…”

Magnetic interactions in La0.7Sr0.3Mn1−Me O3 (Me=Ga, Fe, Cr) manganites

“…Previous studies have shown a gradual destruction of ferromagnetic state upon chemical doping with these ions what has been explained by diminution of double exchange [14][15][16][17][18][19][20]. According to Ref.…”

“…According to Ref. [14][15][16][17][18][19][20] [21] and considered to be optimal for preparation of the high-purity compounds. Neutron diffraction data at ambient pressure and high resolution were collected using the powder diffractometer Е9 (Helmholtz-Zentrum, Berlin).…”