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Neutron Scattering from Magnetic Materials part 12

Tham khảo tài liệu 'neutron scattering from magnetic materials part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Magnetic excitations 327 Table 1 Ordering temperatures Tc spin wave stiffness D zone-boundary magnon energy Ezb and criteria for itinerancy D kTc and EzB kTc of the infinite layer and bilayer manganites along with those of other known itinerant and localized magnetic materials 52 87 Sample Tc K D meV Â2 Ezb meV D Â2 kTc v Ez kTC La0.95Ca0.05MnO3 123.0 3 4.5 1 1.6 001 0.42 0.15 La0.92Ca0.08MnO3 26.0 3 7.3 1 1.6 001 0.67 0.15 La0.67Ca0.33MnO3 250 170 7.9 La0.85Sr0.15MnO3 235 95 2 56 010 4.6 2.76 La0.7Sr0.3MnO3 355 La0.7Ba0.3MnO3 350 152 3 32 100 5.04 1.06 La0.7Pb0.3MnO3 355 133.7 35 100 4.37 1.14 La1.2Sr1.8Mn2O7 128 169 37 100 15.3 3.35 100 Ni 631 550 350 10.1 6.43 Fe 1021 281 800 3.19 9.1 MnSi 40 52 15.8 Ni3Al 41 85 24 Fe3Pt 504 80 1.84 Pd2MnSn 190 100 30 6.10 1.83 Pt3Mn 453 215 80 5.51 2.05 EuO 69 12 6 2.01 1.02 EuS 10.6 2.6 2.3 1.82 1.61 been investigated by inelastic neutron scattering. The neutron scattering investigation of the spin dynamics of the doped ferromagnetic manganites has made considerable progress. We have attempted to summarize the data obtained by neutron scattering in hole-doped manganites along with those of classical metallic itinerant ferromagnets. Mook 52 has suggested the ratios D kTC and EZB kTC as criteria for the itinerancy of the magnetic electrons. Here EZB is the energy of the zone boundary magnon. These two ratios have high values for itinerant electron systems like Fe and Ni and are small for localized systems like EuO and EuS. Table 1 gives the ordering temperature Tc spin wave stiffness D zone-boundary magnon energy Ezb and criteria for itinerancy D kTC and EZB kTC of the infinite-layer and bilayer manganites along with those of other known itinerant and localized magnetic materials. Comparing the ratios kDc and Et of different materials from Table 1 we see that the doped ferromagnetic manganites which are close to the composition at which CMR effects are maximum are of rather itinerant character. Especially the bilayer manganite .