Quantum oscillations in the linear chain of coupled orbits: The organic metal with two cation layers θ-(ET)₄CoBr₄(C₆H₄Cl₂)

¹ Laboratoire National des Champs Magnétiques Intenses (UPR 3228 CNRS, INSA, UJF, UPS) 143 avenue de Rangueil, F-31400 Toulouse, France, EU
² Institut Jean Lamour, Département de Physique de la Matière et des Matériaux, Groupe de Physique Statistique, CNRS-Nancy-Université - BP 70239, F-54506 Vandoeuvre les Nancy Cédex, France, EU
³ Institute of Problems of Chemical Physics, RAS - 142432 Chernogolovka, MD, Russia
⁴ Institut de Ciència de Materials de Barcelona, CSIC, Campus de la UAB - 08193, Bellaterra, Spain, EU

^a alain.audouard@lncmi.cnrs.fr

Received: 17 October 2011
Accepted: 24 January 2012

Abstract

Analytical formulae for de Haas-van Alphen (dHvA) oscillations in linear chain of coupled two-dimensional (2D) orbits (Pippard's model) are derived systematically taking into account the chemical potential oscillations in magnetic field. Although corrective terms are observed, basic (α) and magnetic-breakdown–induced (β and 2β−α) orbits can be accounted for by the Lifshits-Kosevich (LK) and Falicov-Stachowiak semiclassical models in the explored field and temperature ranges. In contrast, the “forbidden orbit” β−α amplitude is described by a non-LK equation involving a product of two classical orbit amplitudes. Furthermore, strongly non-monotonic field and temperature dependence may be observed for the second harmonics of basic frequencies such as 2α and the magnetic breakdown orbit β+α, depending on the value of the spin damping factors. These features are in agreement with the dHvA oscillation spectra of the strongly 2D organic metal θ-(ET)₄CoBr₄(C₆H₄Cl₂).