Origin of magnetism in La and Fe doped SrTiO3−δ films

Abstract

We have studied the magnetic and electrical properties of LaySr1−yTi0.9Fe0.1O3−δ films for compositions where y=0, 0.2, 0.5, and 0.7. All the films exhibited room temperature ferromagnetism with a magnetic moment ranging from 0.7 μB/Fe to 0.2 μB/Fe. The SrTi0.9Fe0.1O3−δ (y=0) sample is an insulator with a small polaron like temperature dependence of resistivity. On the other hand y=0.2 and y=0.5 films exhibited a metallic type of resistivity which can be described by a power law. The largest magnetic moment was observed in the most resistive member (y=0) of the LaySr1−yTi0.9Fe0.1O3−δ family. This is in contrast to the carrier mediated magnetism models. The origin of the magnetism in highly resistive y=0 film could be attributed to the mixed valence state of Fe. On the other hand, La doped sample (y>0) exhibited features of carrier mediated magnetism as well as the mixed valence magnetism. The origin of the observed magnetism in all films has been discussed.

Induction and control of room-temperature ferromagnetism in dilute Fe-doped SrTiO3 ceramics

“…As can be seen from the high temperature M-T curves [Figs. 3(a) and 3(b)], the paramagneticferromagnetic transition temperature (T c ) of SVTF and SFTF is close to that of (Sr 0.8 La 0.2 )Ti 0.9 Fe 0.1 O 3Àd , 16 and T c of SFTF (654 K) is a bit higher than that of SVTF (649 K), agreeing with the stronger magnetism of SFTF. At low temperature and under a magnetic field of 50 Oe [ Fig.…”

“…[9][10][11][12][13] One of the hot spots of magnetically doped materials is the magnetic properties especially at room temperature, which is also the case for materials with Fe substitution. An early study 14 16 agreed with the above mentioned mechanism associated with the mixedvalence-states of Fe ions, their experiments showed that ferromagnetism emerged at less Fe concentration of x ¼ 0.1. Kim et al 13 declared that the epitaxial SrTi 1Àx Fe x O 3 films exhibited RTFM when 0.07 x 0.38, with the doping contents overlapping with the former two.…”

“…Now we try to find the origins of the magnetism in our samples, which are considered to possibly include: Magnetoelastic effect, oxygen vacancies, mixed-valencestate of magnetic ions, and nonlinear bonding. [9][10][11][12][13]16,20,35 Magnetoelastic effect, a mechanism to create magnetic ordering in the absence of exchange interactions, needs appropriate magnetoelastic ions to produce Jahn-Teller distortion as well as enough stress to achieve magnetoelastic Inset of (c) displays the time dependent normalized magnetization of SVTF and SFTF at 14 K and 300 K after a FC procedure (4000 Oe) from 380 K, where M 0 is the magnetization right after the cooling field is removed at target temperatures. coupling, 13 thus it often works in strained epitaxial films.…”

Cobalt–Carbon Complexes Induced Ferromagnetism in Chemically Modified Perovskite Dilute Magnetic Complex Oxides

“…7−9 However, there are very few reports on the magnetism investigations in the LSTO-based DMOs. 10−19 Several irreconcilable origins of FM include intrinsic carriers, 10,11 structural defects, 12−15 mixed valence state, 16 and the presence of secondary phases. 17−19 Although the field has suffered from the intense controversy on the origin of FM, recent considerable efforts have also been devoted to the control of FM in DMOs, for instance, by systematically studying dopant−defect complexes, 20,21 tuning dopant valence states, 22 as well as exerting an electric field.…”

“…Dilute magnetic oxides (DMOs), a class of magnetic semiconductors, are promising supporting materials for future spintronic devices, utilizing both spin and charge degrees of freedom. − Since the first observation of high-temperature ferromagnetism (FM) in Co-doped TiO 2 thin films by Matsumoto et al, intensive research efforts have been devoted to exploring various properties and the origin of FM in DMOs with/without dilute doping of transition metals (TMs) and non-TMs, which have been discussed in detail in recent reviews by Ogale and Dietl. − Complex compounds based on perovskite (La,Sr)TiO 3 (LSTO) are especially appealing in DMOs because, in contrast to TiO 2 and ZnO, they belong to a family of strongly correlated conductors. In such compounds, the La 3+ substitution for Sr 2+ introduces itinerant electrons into the Ti 3d conduction band, allowing independent controls of both the magnetic and carrier (bound or free) doping. − However, there are very few reports on the magnetism investigations in the LSTO-based DMOs. − Several irreconcilable origins of FM include intrinsic carriers, , structural defects, − mixed valence state, and the presence of secondary phases. − …”