D-d Excitations in Transition-Metal Oxides : A Spin-Polarized Electron Energy-Loss Spectroscopy (SPEELS) Study

by Fromme, Barbel

• ISBN13: 9783540410515
• ISBN10: 3540410511
• Format: Hardcover
• Copyright: 2001-02-01
• Publisher: Springer Verlag

Summary

In this monograph, investigations of the electronic structures of the transition-metal oxides MnO, CoO, and NiO with spin-polarized electron energy-loss spectroscopy are presented and compared with other experimental and theoretical results. After a review of the present knowledge of the electronic structure of the monoxides, the spectroscopic method applied and its special advantages are described. The knowledge and use of the different spin, angle, and primary-energy dependences of the various relevant inelastic electron-scattering mechanisms provide new insights into the excitation processes of the optically forbidden transitions between the crystal-field-split 3d states of the bulk and of the surface.

Table of Contents

Introduction	1	(4)
Electronic Structure of MnO, CoO, and NiO	5	(22)
Introduction	5	(1)
Crystal Structure and Optical Gap	6	(6)
3d States and d-d Transitions	12	(15)
Crystal-Field Multiplets	12	(8)
d-d Transitions	20	(2)
Surface Transition-Metal Ions	22	(5)
Electron Energy-Loss Spectroscopy-Inelastic Electron Scattering	27	(24)
Introduction	27	(3)
Electron Scattering	30	(15)
Introduction	30	(2)
Dielectric Dipole Scattering	32	(3)
Impact and Exchange Scattering	35	(6)
Resonant Scattering	41	(4)
Spin-Polarized Electron Energy-Loss Spectroscopy (SPEELS)	45	(6)
Introduction	45	(1)
Spin-Flip and Nonflip Intensity	46	(1)
Spin Flips and Nonflips in Dipole-Forbidden Transitions	47	(4)
Experiment	51	(12)
Experimental Setup	51	(8)
Introduction	51	(2)
GaAs Source	53	(2)
Primary Energy	55	(2)
Target Temperature	57	(1)
Scattering Geometry	57	(1)
Mott Detector	58	(1)
Targets and Target Preparation	59	(4)
NiO	59	(1)
CoO	60	(1)
MnO	60	(3)
SPEELS of Transition-Metal Oxides-Results and Discussion	63	(62)
Introductory Summary	63	(3)
Primary-Energy Dependence and Resonances	66	(19)
Spin-Integrated Energy-Loss Spectra	66	(8)
Other Correlations Between d-d Excitations and Transitions Across the Optical Gap?	74	(4)
Spin-Resolved Measurements	78	(7)
Scattering-Geometry Dependence	85	(18)
Bulk d-d Excitations	85	(11)
Surface d-d Excitations	96	(7)
Antiferromagnetic Order	103	(2)
Half-Order LEED Spots	103	(1)
Influence on d-d Excitations	104	(1)
Assignment of the d-d Excitation Peaks	105	(12)
Introduction	105	(1)
MnO	106	(4)
CoO	110	(4)
NiO	114	(3)
Transitions Across the Optical Gap	117	(8)
Interband and Core-Level Excitations of MnO	117	(3)
Optical Gaps of NiO, CoO, and MnO	120	(5)
Summary	125	(6)
References	131	(12)
Index	143