Lattice effect on magnetism in CMR perovskite La0.85Sr0.15MnOz
- PDF / 389,357 Bytes
- 4 Pages / 578 x 780 pts Page_size
- 87 Downloads / 205 Views
C Springer-Verlag 1997
Lattice effect on magnetism in CMR perovskite La0.85Sr0.15 MnOz N. Zhang1,2 , W. Ding2 ,, W. Zhong2 , K. Du1 , K. Wang1 , Y. Du2 1 Key Lab of Jiangsu Province for Optic & Electric Techniques, Nanjing Normal University, Nanjing 210024, China 2 National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
Received: 20 January 1997/Accepted: 28 February 1997
Abstract. The grain size dependencies of magnetic properties in the granular perovskite La 0.85 Sr 0.15 MnO 3 system has been investigated. Enlargements of lattice parameters with grain growth have been observed. Associated with this growth are a series of magnetic changes, including magnetization, Curie temperature Tc and superparamagnetic behavior. These phenomena may provide another route to understanding the relationship between structure and magnetism in the holedoped manganese perovskites. PACS: 75.50.-y; 61.10.-l; 81.35.+k; 75.60.-d
The discovery of the colossal magnetoresistance (CMR) effect in the family of perovskites La-R-Mn-O (R = Sr , Ca, Pb, Ba) has recently attracted much attention to the electric and magnetic properties of the hole doped magnetic oxides [1–3]. The CMR phenomenon was traditionally attributed to the double-exchange interactions between pairs of Mn 3+ and Mn 4+ ions in these manganese oxides. However, accumulating experimental data demonstrates that doubleexchange is incompatible with many properties. In particular, the model can not be used to explain the coupling between the structure and transport properties of these compounds. Although the exact mechanism of CMR remains plausible, it is now believed that the CMR phenomenon, the transport and magnetic properties in this perovskite related not only to double-exchange but also to the lattice structural distortions. Reports increasingly indicate that structure and magnetism can influence each other. An external field can induce structural variation, phase transition [4] or striction [5], in the compound. Whereas, structural distortion(s) induced by heating [6], pressing [7], A-site ion substitution [8] or oxygen content variation [9], can also change the magnetism, including magnetization M and Curie temperature Tc , thereby changing the resistivity, maybe through double-exchange. It has been found that the Mn-O bond length, Mn-O-Mn bond angle or the structural variation can all greatly influence the magnetic properties of these perovskites [8–10]. Nevertheless, despite the many studies on this subject, structure-
12 June 1997
coupled magnetism in the compound has not been well characterised [11–13]. In this paper, we present the first observations about the structure-dependent magnetic properties in the granular perovskite La 0.85 Sr 0.15 MnO 3 system. We will show grain size dependent structural distortions and change of magnetism, and through the measurement of oxygen stoichiometry, we will demonstrate that the change of magnetism of the sample is dependent not only on oxygen content but also more on lattice distortions. We
Data Loading...
