Manganese monosilicide

Manganese monosilicide (MnSi) is an intermetallic compound, a silicide of manganese. It occurs in cosmic dust as the mineral brownleeite. MnSi has a cubic crystal lattice with no inversion center; therefore its crystal structure is helical, with right-hand and left-hand chiralities.

Manganese monosilicide

MnSi prepared by zone melting
Structures of left-handed and right-handed MnSi crystals (3 presentations, with different numbers of atoms per unit cell)
Names
IUPAC name Manganese silicide
Identifiers
3D model (JSmol)	Interactive image
PubChem CID	49854137
InChI InChI=1S/Mn.Si Key: PYLLWONICXJARP-UHFFFAOYSA-N
SMILES [Si].[Mn]
Properties
Chemical formula	MnSi
Molar mass	83.023 g/mol
Melting point	1,280 °C (2,340 °F; 1,550 K)[1]
Thermal conductivity	0.1 W/(cm·K)[1]
Structure
Crystal structure	Cubic[2]
Space group	P213 (No. 198), cP8
Lattice constant	a = 0.45598(2) nm
Formula units (Z)	4
Hazards
Flash point	Non-flammable
Related compounds
Other cations	Iron silicide Cobalt silicide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N (what is ^YN ?)
Infobox references

MnSi is a paramagnetic metal that turns into a ferromagnet at cryogenic temperatures below 29 K. In the ferromagnetic state, the spatial arrangement of electron spins in MnSi changes with magnetic field, forming helical, conical, skyrmion, and regular ferromagnetic phases.

Crystal structure and magnetism

Magnetic phase diagram of NiSi. At low temperatures, with increasing magnetic field, spins in NiSi form helical, conical, skyrmion (SkS) and regular ferromagnetic spatial structures. At high temperatures the spin orientation is random (paramagnetic)

Simulated and measured (by STXM) images of helical, skyrmion and conical phases in FeGe. All magnetic properties are very similar in FeGe and MnSi, except for T_c values.

Manganese monosilicide is a non-stoichiometric compound, meaning that the 1:1 Mn:Si composition, lattice constant and many other properties vary depending on the synthesis and processing history of the crystal.[2]

MnSi has a cubic crystal lattice with no inversion center; therefore its crystal structure is helical, with right-hand and left-hand chiralities. At low temperatures and magnetic fields, the magnetic structure of NiSi can be described as a stack of ferromagnetically ordered layers lying parallel to the (111) crystallographic planes. The direction of magnetic moment varies from layer to layer by a small angle due to the antisymmetric exchange.[2]

Upon cooling to temperatures below T_c 29 K MnSi changes from a paramagnetic into a ferromagnetic state; the transition temperature T_c decreases with increasing pressure, vanishing at 1.4 GPa.[2]

Electron spins in MnSi show dissimilar, yet regular spatial arrangements at different values of applied magnetic field. Those arrangements are named helical, skyrmion, conical, and regular ferromagnetic. They can be controlled not only by temperature and magnetic field, but also by electric current, and the current density required for manipulating skyrmions (~10⁶ A/m²) is approximately one million times smaller than that needed for moving magnetic domains in traditional ferromagnets. As a result, skyrmions in MnSi have potential application in ultrahigh-density magnetic storage devices.[3]

Synthesis

Centimeter-scale single crystals of MnSi can be prepared by direct crystallization from the melt using the Bridgman, zone melting or Czochralski methods.[2]

References

1. Levinson, Lionel M. (1973). "Investigation of the defect manganese silicide Mn_nSi_2n−m". Journal of Solid State Chemistry. 6 (1): 126–135. doi:10.1016/0022-4596(73)90212-0.
2. Stishov, Sergei M.; Petrova, Alla E. (2011). "Itinerant helimagnetic compound MnSi". Uspekhi Fizicheskih Nauk. 181 (11): 1157. doi:10.3367/UFNr.0181.201111b.1157.
3. Nagaosa, Naoto; Tokura, Yoshinori (2013). "Topological properties and dynamics of magnetic skyrmions". Nature Nanotechnology. 8 (12): 899–911. doi:10.1038/nnano.2013.243.