title: Effect of Rabi splitting on the low-temperature electron paramagnetic resonance signal of anthracite.
abstract: Specific distortions of the EPR signal of bulk anthracite are observed at low temperatures. They are accompanied by variations in the microwave oscillator frequency and are explained by the manifestation of the Rabi splitting due to the strong coupling between electron spins and the cavity, combined with the use of an automatic frequency-control (AFC) system. EPR signals are recorded at negligible saturation in the temperature range of 4-300K with use of the AFC system to keep the oscillator frequency locked to the resonant frequency of the TM110 cylinder cavity loaded with the sample. For the sample with a mass of 3.6mg the line distortions are observed below 50K and increase with temperature lowering. The oscillator frequency variations are used to estimate the coupling strength as well as the number of spins in the sample. It is shown that the spin-cavity coupling strength is inversely proportional to temperature and can be used for the absolute determination of the number of spins in a sample. Our results indicate that at low temperatures even 1016spins of the anthracite sample, with a mass of about 0.5mg, can distort the EPR line.
authors.affiliation: Institute of Physics, University of Szczecin, Szczecin, Poland.
authors.forename: Ryhor
authors.initials: R
authors.lastname: Fedaruk
authors.affiliation: Institute of Molecular Physics, Polish Academy of Sciences, Poznań, Poland.
authors.forename: Roman
authors.initials: R
authors.lastname: Strzelczyk
authors.affiliation: Institute of Molecular Physics, Polish Academy of Sciences, Poznań, Poland; NanoBioMedical Centre, Adam Mickiewicz University, Poznań, Poland.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Tadyszak
authors.affiliation: Scientific-Practical Materials Research Centre NAS of Belarus, Minsk, Belarus.
authors.forename: Siarhei A
authors.initials: SA
authors.lastname: Markevich
authors.affiliation: Institute of Molecular Physics, Polish Academy of Sciences, Poznań, Poland. Electronic address: Maria.Augustyniak@ifmpan.poznan.pl.
authors.forename: Maria Aldona
authors.initials: MA
authors.lastname: Augustyniak-Jabłokow
keywords: Anthracite; EPR; Lineshape distortion; Rabi splitting; Spin counting; Strong spin-cavity coupling