Effects of the Mn/Bi ratio on the magnetic properties of MnBi thin films grown by magnetron co-sputtering

Structural ordering at magnetic seeds with twins at boundaries of a core–shell alloy Mn60Bi40 and tailored magnetic properties

“…Thus, I 110 =0.23, relative to I 101 =1.0 in the initial, is grown to 0.43 and 0.51, at a due loss of I 102 =1.02→0.43 and 0.48 on 24-96 h anneals, respectively, a way at I 110 /I 102 is duly grown in the plots in figure 4(e). An anisotropic growth of XRD peaks is also noticed in MnBi films at R varied 0.84-1.32 in a 〈002〉texture [29]. Further, at anneals in figure 5(C), also Bi (110) peak is shifted towards lower d 110 values, e.g.…”

“…below d 110 =0.2273 nm at pure Bi [37], as even a free Bi has a few Mn (lowers d hkl ) diffused into it as a MnBi 4 type minority phase at its a/c values obey the Vegard's law. Bi-rich islands are shown in elemental maps at the MnBi films [29,39]. At R<1, Bi (012) peak is strong, while Bi (003) and (006) peaks turn up stronger at R→1.32, which are duly shifted over larger '2θ' at larger R = 0.84-1.32 [29].…”

“…Unwantedly, H c declines both at bulk (multidomains) and too tiny SMDs (SPM: superparamagnetic features, H c →0) [8,17,28], as kinetic energy, k B T>K 1 , dominates at individual particles (k B : Boltzmann constant and T: temperature). At films, H c and M r /M s rapidly develop at anneals, in lieu of a SPM→FM phase transforms at critical SMDs [5,29]. In this view, how surface atoms can order at NPs (seeds), how a topological order favors it at FM facets, and how those affect emerging FM properties are open issues of further studies.…”

A core–shell magnet Mn70Bi30 grown at seeds in magnetic fields and its impacts on its spin-dynamics, Curie point and other tailored properties

“…As a result, non-equilibrium processes can take place with a thermal (or other stimuli) induced local atomic/spin ordering at the permeable α-MnBi FM facets at mobile Ts or vacancies. A nonstoichiometry, x ≠ 0, reflects in a lattice either shrinks or expands at a surplus Mn or Bi atoms [32,36]. Elemental mapping of MnBi films (magnetron sputtered) display small islands Mn 50 Bi 50, Mn 60 Bi 40 , or Mn 63 Bi 37 surrounded by finer Mn/Bi-rich clusters of different phases at a micro-to-nanoscale [28,36].…”

“…A nonstoichiometry, x ≠ 0, reflects in a lattice either shrinks or expands at a surplus Mn or Bi atoms [32,36]. Elemental mapping of MnBi films (magnetron sputtered) display small islands Mn 50 Bi 50, Mn 60 Bi 40 , or Mn 63 Bi 37 surrounded by finer Mn/Bi-rich clusters of different phases at a micro-to-nanoscale [28,36].…”