Magnetic dynamics of bilayer manganite La1.4Sr1.6Mn2O7

Abstract

U ovom radu je istraživana magnetska dinamika dvoslojnog manganita La1.4Sr1.6Mn2O7 mjerenjem linearne i nelinearne izmjenične susceptibilnosti na temperaturama izmedu 4.2 K i 400 K, te magnetizacije izmedu 320 K i 500 K. Dokazano je postojanje Griffithsove faze na 370 K, dugodosežnog magnetskog uređenja na 91.2 K, te pojava staklastog ponašanja na temperaturama nižima od uređenja, s temperaturom ostakljivanja od 26.4 K. Također, uočeno je pet feromagnetskih prijelaza između 250 K i 320 K, koje pripisujemo kristalnim defektima. Predložen je model prema kojem su defekti zaslužni za metalnu vodljivost duž c kristalnog smjera na temperaturama ispod magnetskog uređenja.The magnetic dynamics of the bilayer manganite La1.4Sr1.6Mn2O7 was investigated by measuring the linear and nonlinear AC susceptibility between 4.2 K and 400 K, and magnetization between 320 K and 500 K. It was proven that a Griffiths-like phase appears at 370 K, and that long range order is set at 91.2 K. Bellow the ordering temperature the system behaves as a reentrant spin glass, with the freezing temperature of 26.4 K. Also, there are five ferromagnetic transitions between 250 K and 320 K, which are attributed to crystal defects. We propose a model according to which these defects cause the metallic conduction in the c crystallographic direction in the magnetically ordered phase