Magnetic spin resonance inCeB6

Abstract

Line shape of magnetic spin resonance at 60 GHz specific to the phase II ͑so-called antiferroquadrupole phase͒ of CeB 6 was studied. The applied procedure of data analysis has allowed obtaining g factor of the oscillating magnetic moments, line width, and oscillating magnetization. It is found that the approaching to the transition temperature T I-II from phase II to the paramagnetic phase I results in strong broadening of the resonance ͑the line width increases three times in the range 1.8 K Յ T Յ 3.8 K͒ whereas g factor g = 1.59 remains temperature independent. Magnetic-resonance data suggests that the magnetization of CeB 6 in the phase II consists of several contributions, one of which is responsible for the observed magnetic resonance. This term in magnetization is missing in the paramagnetic phase and corresponds to ferromagnetically interacting localized magnetic moments. The magnitude of the oscillating part of magnetization is less than total magnetization in the range T ‫ء‬ Յ T Յ T I-II and coincides with the total magnetization for T Յ T ‫ء‬ , where T ‫ء‬ ϳ 2 K. We argue that ferromagnetic correlations play a key role in the observed phenomenon in analogy with the recent experimental and theoretical results on the magnetic resonance in the dense Kondo systems. At the same time the interpretation of the magnetic-resonance data in the framework of the existing models of magnetism in CeB 6 faces substantial difficulties, which demands further development of the theory of static and dynamic magnetic properties of this heavy fermion metal.

Theory of Electron Spin Resonance in Ferromagnetically Correlated Heavy Fermion Compounds

“…Furthermore, the ferromagnetic correlations enhance the susceptibility (in agreement with experiment where χ 0 displays a kink 43,50 ) and hence reduce the line width of the resonance, which then becomes accessible to observation.…”

Angular Dependences of ESR Parameters in Antiferroquadrupolar Phase of CeB6

“…The AFQ phase at zero magnetic field develops below T Q = 3.2 K. Further temperature decrease transfers this compound into AFM phase below T N = 2.4 K. Magnetic field application stabilizes the AFQ phase causing an increase of T Q as well as a suppression of AFM order below T N . The experimental observation of ESR in CeB 6 [1][2][3] induced a novel theoretical approach describing ESR in the AFQ phase [5,6]. It is based on the consideration of Γ 8 state of Ce 3+ ions forming two orbitally ordered sublattices.…”

“…Electron spin resonance (ESR) in heavy fermion compound CeB 6 [1][2][3] is a puzzling phenomenon forming new aspects in the investigation of the exotic low temperature state of this system. Strong exchange interaction of local moments with conduction electrons prevents the observation of the resonance behavior of Ce 3+ ions in metals and only few systems exhibiting ESR have been reported so far ( [4] and references therein).…”

“…This model explains the observation of a single ESR line instead of four lines expected for Γ 8 state and it predicts an angular dependence of the g-factor. It is worth noting that up to now ESR in CeB 6 has been studied exclusively for magnetic field applied in [110] crystallographic direction [1][2][3] and that measurements of ESR anisotropy could not just examine the relevance of the theory but also clarify the magnetic state of Ce 3+ ion in CeB 6 . * corresponding author; e-mail: semeno@lt.gpi.ru…”

Electron spin resonance of the ferromagnetic Kondo lattice CeRuPO

“…This paper reports detailed ESR investigations of CeRuPO in order to document the properties of the rarely observed Ce 3+ spin resonance (we are aware of only two others, namely CeP [9] and CeB 6 [10]), and to show the effect of ferromagnetic correlations and magnetic order on the Kondo ion spin resonance.…”