Spin liquids and spin glasses in Mn-based alloys with the cubic A13 (βMn) structure

•As-cast samples of doped and undoped Mn100−xZx with Z = Al, Ge, Fe have the beta-Mn structure.•Only the undoped sample is a spin liquid, all others are spin glasses.•Andreev reflection reveals a spin polarization of 8% in the spin glass, but none in the spin liquid.•Fixed spin moment DFT calculatio...

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Bibliographic Details
Published in:Journal of magnetism and magnetic materials 2020-05, Vol.501, p.166429, Article 166429
Main Authors: Zhang, Rui, Gercsi, Zsolt, Venkatesan, M., Jha, Ajay, Stamenov, Plamen, Coey, J.M.D.
Format: Article
Language:English
Subjects:
Aluminum
Andreev reflection
Bifurcations
Freezing
Ingot casting
Iron
Low temperature
Magnetic permeability
Magnetic susceptibility
Manganese base alloys
Point contact
Polarization (spin alignment)
Spin glass
Spin glasses
Spin liquid
Zero point energy
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Summary:•As-cast samples of doped and undoped Mn100−xZx with Z = Al, Ge, Fe have the beta-Mn structure.•Only the undoped sample is a spin liquid, all others are spin glasses.•Andreev reflection reveals a spin polarization of 8% in the spin glass, but none in the spin liquid.•Fixed spin moment DFT calculations show an unusual broad and shallow energy minimum for beta Mn moments from 0 to 0.4 µB.•The depth of the energy minimum, approximately 0.5 meV/atom, is a lower limit on the zero-point energy. As-cast ingots of Mn100−xZx with Z = Al, Ge, Mn, Fe and Co all have the A13 βMn structure up to some maximum value of x. The magnetic susceptibility of pure βMn is ≈ 9 × 10−4 from 4 to 400 K, but the field-cooled and zero-field-cooled susceptibilities of all doped samples increase at low temperature and they bifurcate at a spin-freezing temperature Tf that increases with x, linearly at first. Point contact Andreev reflection shows evidence of a net spin polarization in a spin glass sample but not in the pure βMn spin liquid. Fixed-moment density functional calculations indicate a very shallow energy minimum (< 1 meV/atom) for the 12d-site Mn moment that extends from x = 0 to 0.4 µB. The minimum energy is interpreted as a lower limit on the zero-point energy.
ISSN:0304-8853
1873-4766
DOI:10.1016/j.jmmm.2020.166429