Hyperfine interactions in MnAs studied by perturbed angular correlations of gamma-rays using the probe Br-77 -> Se-77 and first-principles calculations for MnAs and other Mn pnictides

authors	Goncalves, JN; Amaral, VS; Correia, JG; Lopes, AML
nationality	International
journal	PHYSICAL REVIEW B
keywords	MAGNETOOPTICAL PROPERTIES; ELECTRONIC-STRUCTURE; MAGNETIC-PROPERTIES; PHASE-TRANSITION; TRANSFORMATION; FIELDS; ANISOTROPY; MOSSBAUER; COMPOUND; PRESSURE
abstract	The MnAs compound shows a first-order transition at T-C approximate to 42 degrees C, and a second-order transition at T-t approximate to 120 degrees C. The first-order transition, with structural (hexagonal-orthorhombic), magnetic (FM-PM), and electrical conductivity changes is associated to magnetocaloric, magnetoelastic, and magnetoresistance effects. We report a study in a large temperature range from -196 degrees up to 140 degrees C, using the gamma-gamma perturbed angular correlations method with the radioactive probe Br-77 --> Se-77, produced at the On-Line Isotope Mass Separator (ISOLDE)-CERN facility. The electric field gradients and magnetic hyperfine fields are determined across the first-and second-order phase transitions encompassing the pure and mixed phase regimes in cooling and heating cycles. The temperature irreversibility of the first-order phase transition is seen locally at the nanoscopic scale sensitivity of the hyperfine field, by its hysteresis, detailing and complementing information obtained with macroscopic measurements (magnetization and X-ray powder diffraction). To interpret the results hyperfine parameters were obtained with first-principles spin-polarized density functional calculations using the generalized gradient approximation with the full potential (linear) augmented plane wave plus local orbitals method (WIEN2K code) by considering the Se probe at both Mn and As sites. A clear assignment of the probe location at the As site is made and complemented with the calculated densities of states and local magnetic moments. We model electronic and magnetic properties of the chemically similar MnSb and MnBi compounds, complementing previous calculations.
publisher	AMER PHYSICAL SOC
issn	1098-0121
year published	2011
volume	83
issue	10
digital object identifier (doi)	10.1103/PhysRevB.83.104421
web of science category	Physics, Condensed Matter
subject category	Physics
unique article identifier	WOS:000288895900001