Spin freezing and magnetic inhomogeneities in bilayer manganites
Physical Review Letters 89 (2001) 277601 4pp
Colossal magnetoresistance in the layered chromium sulfide Cr2 S3-x (x=0.08)
Physical Review B - Condensed Matter and Materials Physics 64:13 (2001) 1324021-1324024
Abstract:
We report structural, magnetic, and magnetotransport properties of the two-dimensional chromium sulfide Cr2S2.92, which contains both Cr3+ and Cr2+ ions. Below its magnetic-ordering temperature (TN=118 K), Cr2S2.92 exhibits a weak spontaneous magnetization with a maximum around 90 K and a value of 0.013(4) μB per Cr ion at 5 K. The resistivity and magnetoresistance exhibit pronounced local maxima around TN (MR=48% in a field of 14 T). The magnetotransport properties are discussed in terms of magnetic-polaron formation.Chemically induced magnetism and magnetoresistance in La(0.8)Sr(1.2)Mn(0.6)Rh(0.4)O(4).
J Am Chem Soc 123:31 (2001) 7610-7615
Abstract:
It is shown by magnetometry and microSR spectroscopy that short-range magnetic interactions between the Mn cations in the nonmetallic K(2)NiF(4)-like phase La(0.8)Sr(1.2)Mn(0.6)Rh(0.4)O(4) become significant below approximately 200 K. Negative magnetoresistance (rho/rho(0) approximately 0.5 in 14 T at 108 K) is apparent below this temperature. Neutron diffraction has shown that an applied magnetic field of 5 T is sufficient to induce saturated (3.38(7)mu(B) per Mn) long-range ferromagnetic ordering of the atomic moments at 2 K, and that the induced ordering persists up to a temperature of 50 K in 5 T. Spin glass behavior is observed below 20 K in the absence of an applied field. The induced magnetic ordering is attributed to the subtle changes in band structure brought about by the external field, and to the controlling influence of Rh(3+) over the relative strength of competing magnetic exchange interactions.Synthesis, structural chemistry and magnetic properties of La1+x A1-x InMnO6-δ : A = Ba, Sr; x = 0, 0.2
Journal of Materials Chemistry 11:6 (2001) 1656-1661
Abstract:
A series of novel double perovskites La1+xA1-xInMnO6-δ (A = Sr, Ba) has been prepared and the room temperature crystal structures have been refined using X-ray and neutron powder diffraction. In all cases the B-site is occupied by a disordered arrangement of In3+ and Mn3+/4+ cations. However, whereas La1+xBa1-xInMnO6-δ exhibits two octahedral tilts and exists in a body-centred cell, space group Imma, La1+xSr1-xInMnO6-δ adopts the three-tilt GdFeO3 structure and has a primitive orthorhombic structure, space group Pnma. Magnetic susceptibility data show that all the compositions synthesised exhibit a spin glass freezing transition at ∼8 K. A negative magnetoresistance Δρ/ρ0 = 10.5% was measured at 164 K in a field of 14 T.Control of magnetic ordering by Jahn--Teller distortions in Nd(2)GaMnO(6) and La(2)GaMnO(6).
J Am Chem Soc 123:6 (2001) 1111-1122