“…Interest in mixed Mn/Ru phases was aroused by the observation that doping insulating, charge-ordered n = ∞ (i.e., perovskite) manganates with low concentrations of Ru can induce ferromagnetism and metalicity. − Ganguly et al have subsequently shown that the introduction of Ru into La 0.5 Sr 1.5 MnO 4 and LaSr 2 Mn 2 O 7 also causes an increase in magnetization while destroying charge ordering; they noted that Ru was less soluble in the n = 1 or 2 materials than in the n = ∞ perovskites. Sharma et al were able to prepare the La-free phase Sr 3 MnRuO 7 and found indications of a ferromagnetic transition coincident with an insulator−metal transition at approximately 66 K. However, the neutron diffraction and magnetometry data presented below demonstrate that although the magnetic susceptibilities of Sr 3 MnRuO 7 and the analogous n =1 phase Sr 2 Mn 0.5 Ru 0.5 O 4 show complex behavior as a function of temperature, neither compound exhibits long-range magnetic order at 2 K; the magnetometry data must be interpreted in terms of spin-glass or cluster-glass behavior. 1 Crystal structures of Ruddlesden−Popper phases n = 1 and n = 2.…”
Polycrystalline samples of Sr 3 MnRuO 7 and Sr 2 Mn 0.5 Ru 0.5 O 4 have been synthesized and characterized by neutron diffraction, dc magnetometry, and magnetotransport measurements. They are, respectively, n ) 2 and n ) 1 members of the Ruddlesden-Popper (RP) A n+1 B n O 3n+1 family; both have tetragonal (I4/mmm) symmetry and a disordered distribution of Ru and Mn over the six-coordinate sites within the perovskite layers of the RP structure. Neither compound shows long-range magnetic order at 2 K, but a spin-glass transition is observed at 16 K (n ) 1) or 25 K (n ) 2). In the case of the n ) 2 compound only, the magnetic transition is accompanied by a reduction in the zero-field electrical conductivity. A maximum magnetoresistance of ∼8% in 14 T is found in both compounds.
“…Interest in mixed Mn/Ru phases was aroused by the observation that doping insulating, charge-ordered n = ∞ (i.e., perovskite) manganates with low concentrations of Ru can induce ferromagnetism and metalicity. − Ganguly et al have subsequently shown that the introduction of Ru into La 0.5 Sr 1.5 MnO 4 and LaSr 2 Mn 2 O 7 also causes an increase in magnetization while destroying charge ordering; they noted that Ru was less soluble in the n = 1 or 2 materials than in the n = ∞ perovskites. Sharma et al were able to prepare the La-free phase Sr 3 MnRuO 7 and found indications of a ferromagnetic transition coincident with an insulator−metal transition at approximately 66 K. However, the neutron diffraction and magnetometry data presented below demonstrate that although the magnetic susceptibilities of Sr 3 MnRuO 7 and the analogous n =1 phase Sr 2 Mn 0.5 Ru 0.5 O 4 show complex behavior as a function of temperature, neither compound exhibits long-range magnetic order at 2 K; the magnetometry data must be interpreted in terms of spin-glass or cluster-glass behavior. 1 Crystal structures of Ruddlesden−Popper phases n = 1 and n = 2.…”
Polycrystalline samples of Sr 3 MnRuO 7 and Sr 2 Mn 0.5 Ru 0.5 O 4 have been synthesized and characterized by neutron diffraction, dc magnetometry, and magnetotransport measurements. They are, respectively, n ) 2 and n ) 1 members of the Ruddlesden-Popper (RP) A n+1 B n O 3n+1 family; both have tetragonal (I4/mmm) symmetry and a disordered distribution of Ru and Mn over the six-coordinate sites within the perovskite layers of the RP structure. Neither compound shows long-range magnetic order at 2 K, but a spin-glass transition is observed at 16 K (n ) 1) or 25 K (n ) 2). In the case of the n ) 2 compound only, the magnetic transition is accompanied by a reduction in the zero-field electrical conductivity. A maximum magnetoresistance of ∼8% in 14 T is found in both compounds.
“…The physical properties of these phases, especially the electric transport and magnetic properties, are known to depend upon the nature and balance state of the ions at A and B sites, B-O-B bond angle, oxygen content and so on. It has been observed that large variation in properties is observed in many cases with partial substitution at the sites A and B (Mahesh et al 1996;Morimoto et al 1996;Sharma and Magotra 1999;Shilovo et al 2002;Sharma et al 2005).…”
Three new phases with compositions, LaSr 2 FeTiO 7 , NdSr 2 FeTiO 7 and GdSr 2 FeTiO 7 , were prepared by the traditional ceramic method. Lazy-Pulverix analysis of the X-ray diffraction data suggests that the phases crystallize in the RP-type (n = 2) structure in the space group, I4/mmm. The cell dimensions along the c-axis decrease with decrease in size of the rare earth ions. Electrical resistivity, as a function of temperature, shows that the materials are insulators and the resistivity decreases with decrease in the size of the rare earth ion, which is attributed to increase in the three-dimensional character.
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