Implications of the B20 crystal structure for the magnetoelectronic structure ofMnSi

Abstract

Due to increased interest in the unusual magnetic and transport behavior of MnSi and its possible relation to its crystal structure (B20) which has unusual coordination and lacks inversion symmetry, we provide a detailed analysis of the electronic and magnetic structure of MnSi. The non-symmorphic P213 spacegroup leads to unusual fourfold degenerate states at the zone corner R point, as well as "sticking" of pairs of bands throughout the entire Brillouin zone surface. The resulting Fermi surface acquires unusual features as a result of the band sticking. For the ferromagnetic system (neglecting the long wavelength spin spiral) with the observed moment of 0.4 µB/Mn, one of the fourfold levels at R in the minority bands falls at the Fermi energy (EF ), and a threefold majority level at k=0 also falls at EF . The band sticking and presence of bands with vanishing velocity at EF imply an unusually large phase space for long wavelength, low energy interband transitions that will be important for understanding the unusual resistivity and far infrared optical behavior.

Chiral modulations and reorientation effects in MnSi thin films

“…63 Thus, the experimentally determined magnetic moment that is 0.39 μ B /Mn in bulk MnSi is enhanced to about S exp = 0.42μ B /Mn in the epitaxial films with a slight volume expansion. As in previous DFT calculations on MnSi with B20-structure, 62 we find a net spin moment of S DFT = 1.00μ B /Mn. As a result of the enhanced spin moment in the DFT calculations that neglect quantum-dynamical spin fluctuations, the MAE is also overestimated.…”

“…The calculated results for the cubic MnSi structure are in good agreement with earlier DFT studies. 62 In the rhombohedrally distorted cell, the site positions 4a for the Mn and Si in the cubic structure are split into two crystallographic inequivalent positions 1a and 3b. For each rhombohedral angle = π/2 − 2(ǫ ⊥ − ǫ )/3, the lattice cell of the distorted bulk MnSi was first optimized by a scalar relativistic calculation.…”

Importance of thermal disorder and electronic occupation for temperature dependence of optical conductivity in FeSi and MnSi

“…11,12 The experimental moment for MnSi, about 0.4 B / f.u., is a factor of 2 smaller than what is found from band calculations ͑which do not search for the possibility of helical spin order͒ at the calculated equilibrium lattice constant. 13,14 Recent studies of MnSi with the technique of x-ray absorption suggest a correlated excite state, and the interpretation in terms of band structure is complicated by the involvement of a core hole. 12 However, through high-resolution optical measurements, it has been possible to detect T-dependent details of the band structure in several B20 compounds.…”

Электронная структура и магнитный фазовый переход в MnSi

“…При этом в рассматриваемой сильно коррелирован-ной электронной системе формируется геликоидаль-ное упорядочение с аномально большими магнитны-ми периодами (порядка 100−1000 ¦ ) [6][7][8], вследствие чего описание электронной структуры сталкивается с заметными трудностями учета длиннопериодической спиновой подсистемы (M q 0 = 0). Поэтому в ab initio LDA + U + SO-расчетах электронной структур [3,[9][10][11] пренебрегают ДМ-взаимодействием и получают основ-ное ферромагнитное состояние для MnSi. Модельный учет в рассматриваемом ферромагнитном основном со-стоянии ДM-взаимодействия приводит к представлениям о ферромагнитном геликоиде, описываемом моделью Янсена−Бака [6,7].…”

“…Известная из LDA + U + SO-расчетов спиновая система является ферромагнитной, а электронная структура представляет собой расщеп-ленные по направлениям спина спин-поляризованные подзоны с раздвижкой, пропорциональной намагничен-ности [3,[9][10][11]. Однако учет ДМ-взаимодействия " закру-чивает" спины, и однородная намагниченность должна исчезать.…”