Effect of Ru doping inLa0.5Sr0.5MnO3and

Abstract

We investigated the structural, magnetic, and transport properties of polycrystalline doping systems La 0.5 Sr 0.5 Mn 1−x Ru x O 3 ͑0 ഛ x ഛ 0.15͒ with ferromagnetic matrix and La 0.45 Sr 0.55 Mn 1−y Ru y O 3 ͑0 ഛ y ഛ 0.5͒ with antiferromagnetic matrix. X-ray photoelectron spectroscopy shows that Ru ions exist mainly in the form of Ru 4+ while there also exist a small quantity of Ru 5+ . For the low doping samples ͓0.05ഛ x͑y͒ ഛ 0.15͑0.2͔͒, the ferromagnetism is enhanced and Curie temperature T C rises with increasing Ru doping level, but T C is much higher than the temperature T IM corresponding to insulating-metallic transition. For the high doping samples ͑0.3ഛ y ഛ 0.5͒, oppositely the ferromagnetism is suppressed and the insulating property is enhanced with further increasing Ru doping level. These results show that there is an exchange interaction between Mn 3+ and Ru 4+ ͑Ru 5+ ͒. The electron spin resonance spectra clearly and directly inspect that the interaction between Mn 3+ and Ru 4+ ͑Ru 5+ ͒ is ferromagnetic. Furthermore, the electron spin resonance spectra also show that a Ru-Ru antiferromagnetic interaction takes place in the high doping region ͑y = 0.4, 0.5͒. We explained the disagreement between T C and T IM .

Magnetic properties and Griffiths singularity in La0.45Sr0.55 Mn1−xCoxO3

“…2. We have investigated the parent sample La 0.45 Sr 0.55 MnO 3 in a previous work [32]. The magnetization increases swiftly as temperature is lowered, exhibiting a robust paramagnetic (PM)-FM transition at T C ¼290 K. However, below 210 K, an abrupt decrease of the magnetization occurs.…”

“…La 0.45 Sr 0.55 MnO 3 lies at the boundary between FM and AFM phases in the phase diagram of La 1À y Sr y MnO 3 and reveals both ferromagnetism and antiferromagnetism. There exists the competition between AFM and FM interactions [32]. Burgy et al and Magen et al [24,36,37] suggested theoretically that the existence of competing phases stabilizes and enhances the FM Griffiths effect.…”

“…Even though many works [22][23][24][25][26][27]32] studied the Griffiths effect in manganites, the doubt of its validity still exists [40]. For example, the application of Griffiths model in manganites accompanies lack of mathematical rigidity.…”

Effect of Fe Substitution on the Physical Properties of La0.62Er0.05Ba0.33Mn1−xFexO3(x = 0.00, 0.05 and 0.15)

“…The magnetic moment gradually reduces. Such irreversibility in the M-T data for the FC and ZFC measurements was observed in several manganite systems and it was suggested that this irreversibility is possibly due to the canted nature of the spins or due to the random freezing of spins [34]. This can be seen clearly at low temperature for x = 0.15, which is generally related to a spin-glass or cluster-glass state.…”

Structural, electric and magnetic properties of La1−xSrxCo1−xRuxO3 (0≤x≤0.6) solid solution

“…The peak at lower energy (282 eV) is associated to the Ru 4+ ion in the Ru based perovskite. 40 The value of ∆E SO corresponding to a peak at higher energy is smaller than that of Ru 4+ . Higher oxidation state Ru 5+ results in weak spin-orbit coupling and hence, confirms the existence of Ru 5+…”