UVSOR Lunch Seminar (2004-09)

Date&Time: February 23, 11:10-11:45
Place: UVSOR Build. #304 (User's room)

Speaker: Dr. Joerg Sichelschmidt

Affiliation: Max-Planck-Institute for Chemical Physics of Solids, Dresden, Germany

Title: Kondo-ion electron spin resonance of isotope clean ¹⁷⁴YbRh₂Si₂


Abstract:
The heavy-fermion compound YbRh₂Si₂ is located very close to a magnetic
field induced quantum critical point. The unexpected observation of electron
spin resonance (ESR) of the Kondo-ion Yb³⁺ below the Kondo temperature
(T_K ~ 25 K) contradicts the itinerant scenario of quantum criticality. The
ESR of isotope clean ¹⁷⁴YbRh₂Si₂ shows a T behavior which is very similar
compared to that of YbRh2Si2. Especially, for the ESR linewidth a progressive
reduction by decreasing T could be confirmed in ¹⁷⁴YbRh₂Si₂. However,
¹⁷⁴YbRh₂Si₂ shows a smaller residual linewidth and a strongly reduced thermal
line broadening in the whole T region. Together with our previous finding that
introducing disorder in YbRh₂Si₂ by La- or Ge-doping causes a more effective
Yb³⁺ ESR relaxation the question arises whether an ESR bottleneck effect could
be responsible for the extremely narrow linewidth.