Magnetoresistance and magnetic properties of La1−x□xMnO3−δ  thin films

Abstract

Epitaxial thin films of La1−x⧠xMnO3−δ(0≤x≤0.33) where ⧠ is a vacancy have been grown on (100) SrTiO3 substrates by pulsed laser deposition. The lanthanum deficiency results in self doping of the system without the need for divalent ion substitution. Both the films and the bulk targets used for deposition were ferromagnetic and showed giant magnetoresistance (GMR). The films increased in saturation magnetization Ms and Curie temperature Tc with increasing x. The Tc, however, was about the same as found in Cax substitutions. Bulk samples showed little change in Ms and Tc with vacancy concentration. Ms in bulk samples is about half the value found in the films which have theoretical saturations for x≥0.2. GMR in the films is a few hundred percent but the bulk values are 25% at H=1.8 T.

Intrinsic insulating ferromagnetism in manganese oxide thin films

“…The unexpected ferromagnetism was considered to be extrinsic and deficiency of La [10,14] was suggested as a possible explanation to it. However, it is not consistent with the fact that FM phase in the LMO thin films with cation deficiency tends to be metallic [7,15,16]. Previous models [17,18] and recent first-principles studies [19,20] on LMO thin films predicted the metallic FM phase, instead of the experimentally observed insulating FM phase.…”

Magnetoresistance and phase composition of La-Sn-Mn-O systems

“…Results of the CMR in La 1Ϫx MnO 3 and LaMnO 3ϩ␦ have been reported recently. [16][17][18] Our work also indicates that La 0.9 MnO 3ϩ␦ has a S-M transition at Tϭ240 K, a paramagnetic-ferromagnetic transition at Tϭ250 K, and the CMR is about 26% in H ϭ15 kOe at Tϭ240 K. 19 Hence, the CMR in La 1Ϫx Sn x MnO 3ϩ␦ may have its origin in a deficiency of La and/or Mn ions for the ABO 3 phase.…”

Oxygen Deficiency Effects upon Structural, Magnetic and Electrical Properties of Doped Manganite Oxides

“…In order to study the vacancy effect upon the Curie temperature, we have plotted in Fig. 6 [18] and La 1± ±x Sr x MnO 3 [13]. Both of the two non-stoichiometric solutions show a shift to lower temperatures in the T C values.…”

“…The Mn 3+ and Mn 4+ concentrations are varied by changing the A doped level or by creating vacancies in A [18] and B [19] or in the oxygen sites. Few works on oxygen deficiency have been realized.…”