Journal of the Physical Society of Japan · 2010 · 17 citations · 16 references
Natural SciencesMaterials SciencePhysicsCondensed Matter PhysicsMagnetic MaterialsSolid State PhysicsFerromagnetismMagnetic Properties Of SolidsMagnetism In SolidsPhase TransitionsSolid-state Phase TransitionsX-ray CrystallographyFirst-order Magnetic TransitionsFirst-order Phase TransitionsMagnetic Order ParametersMagnetic Ordering StudiesMagnetic Phase TransitionsMagnetostructural TransitionsStructural Phase TransitionsTemperature Dependence
Employing neutron and resonant x-ray scatterings, we have investigated the magnetic and structural phase transitions of a high quality single crystal of undoped pnictide EuFe2As2 to reveal the nature of these transitions. It has been found that structural order parameter delta = (a - b)/(a + b) and the square of Fe magnetic order parameter have the same temperature dependence, which is attributed to the linear-quadratic coupling between structural and Fe magnetic order parameters in the Landau free-energy expansion. This result also suggests that Fe magnetic order drives the structural phase transition which is the weak first-order phase transition.
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