Double metal-insulator peaks and effect of Sm3 substitution on magnetic and transport properties of hole-doped La0.85Ag 0.15MnO3

• الحاوية / القاعدة: Journal of Magnetism and Magnetic Materials
• المؤلف الرئيسي: 2-s2.0-79956067286
• التنسيق: مقال
• اللغة: English
• منشور في: 2011
• الوصول للمادة أونلاين: https://www.scopus.com/inward/record.uri?eid=2-s2.0-79956067286&doi=10.1016%2fj.jmmm.2011.03.027&partnerID=40&md5=80fa4e3964560ba3bdff85d9c328a054

La0.85-xSmxAg0.15MnO3 (x=0-0.2) ceramics were prepared using the conventional solid-state synthesis method to investigate the effect of Sm3 substitution on magnetic and electrical transport properties. Magnetic susceptibility versus temperature measurements showed all samples exhibit ferromagnetic to paramagnetic transition with Curie temperature, Tc decreasing from 283 K (x=0) to 164 K (x=0.2) with increasing Sm3. The observed slope in susceptibility, χ′ versus temperature curves below Tc indicates the possible presence of FM and AFM phases in the metallic region. In addition, a deviation from the CurieWeiss law above Tc in 1/χ′ versus T curves indicates the existence of a Griffiths phase in the x=0.05-0.2 samples due to the Sm 3 ion substitution. The Griffith temperature, TG was found to decrease from 295 K (x=0.05) to 229 K (x=0.2). Electrical resistivity measurements of the samples in zero field showed transition from metallic behavior to insulating behavior as the temperature was increased. For x=0, two metalinsulator, MI transition peaks were observed at Tp1=282 K and at Tp2=250 K. Both peaks shifted to lower temperatures with the increase in Sm3. The relative resistivity of the first peak to the second peak decreases with increasing Sm3 for x>0.05 while at x=0.2 the Tp1 peak was strongly suppressed. Magnetoresistance, MR was observed to weaken with Sm3 substitution. The metallic region of the ρ(T) curve of the x=0-0.15 samples was fitted to the model of electronelectron and electronmagnon scattering while the insulating region was fitted to the variable range hopping, VRH model. The resistivity behavior indicated that the substitution of Sm3 weakened the double exchange process and enhanced the JahnTeller effect. Our results indicated that the Tp1 peak is strongly related to the double-exchange mechanism while the Tp2 peak is suggested to originate from magnetic inhomogeneity. © 2011 Elsevier B.V.