Conduction electron spin resonance in AlB2

L M Holanda,Z Fisk,C Rettori,L Mendonça-Ferreira,G M Dalpian,R A Ribeiro,P G Pagliuso,R R Urbano,J M Osorio-Guillén,K Kuga,S Nakatsuji

doi:10.1088/0953-8984/25/21/216001

Abstract

This work reports on electron spin resonance experiments in oriented single crystals of the hexagonal AlB2 diboride compound (P6/mmm, D16h structure) which display conduction electron spin resonance. The X-band electron spin resonance spectra showed a metallic Dysonian resonance with g-value and intensity independent of temperature. The thermal broadening of the anisotropic electron spin resonance linewidth ΔH tracks the T-dependence of the electrical resistivity below T ≃ 100 K. These results confirm the observation of a conduction electron spin resonance in AlB2 and are discussed in comparison with other boride compounds. Based on our main findings for AlB2 and the calculated electronic structure of similar layered honeycomb-like structures, we conclude that any array of covalent B–B layers potentially results in a conduction electron spin resonance signal. This observation may shed new light on the nature of the non-trivial conduction electron spin resonance-like signals of complex f-electron systems such as β-YbAlB4.

Highlights

IntroductionA plausible explanation for this fact is related to the complexity of the Fermi surfaces of these metallic compounds which may give rise to a large distribution of g-values as well as the strong spin–orbit scattering of the conduction electrons (ce) responsible for the broadening of the CESR signal (known as the wipe out effect)
The family of metallic diborides has attracted great interest from the global scientific community after the discovery of superconductivity in MgB2 with highest BCS transition temperature, Tc = 39 K [1]
In summary we have observed the CESR in AlB2 with similar features to those reported for the CESR in MgB2 and graphite intercalated compounds (GIC)

Summary

Introduction

A plausible explanation for this fact is related to the complexity of the Fermi surfaces of these metallic compounds which may give rise to a large distribution of g-values as well as the strong spin–orbit scattering of the conduction electrons (ce) responsible for the broadening of the CESR signal (known as the wipe out effect). The combination of these two effects usually set the CESR beyond the detection limit of a conventional ESR spectrometer [8, 14,15,16], despite the existence of a theoretical prediction of CESR in metals with heavy elements by Fredkin and Freedman based on a model of motional narrowing and many body effects [17, 18]

Results

Discussion

Conclusion