Title: Spin-polaron transport and magnetic phase diagram of iron monosilicide
Authors: Glushkov, VV ×
Voskoboinikov, IB
Demishev, SV
Krivitskii, IV
Menovsky, A
Moshchalkov, Victor
Samarin, NA
Sluchanko, NE #
Issue Date: 2004
Series Title: Journal of experimental and theoretical physics vol:99 issue:2 pages:394-414
Conference: date:Russian Acad Sci, Prokhorov Inst Gen Phys, Moscow 119991, Russia; Moscow Inst Phys & Technol, Dolgoprudnyi 141700, Moscow Oblast, Russia; Univ Amsterdam, Van Der Waals Zeeman Lab, NL-1018 XE Amsterdam, Netherlands; Katholieke Univ Leuven, Vaste Stof Fys Magnetisme Lab, B-3001 Heverlee, Belgium
Abstract: The study of galvanomagnetic, magnetic, and magnetooptical characteristics of iron monosilicide in a wide range of temperatures (1.8-40 K) and magnetic fields (up to 120 kOe) has revealed the origin of the low-temperature sign reversal of the Hall coefficient in FeSi. It is shown that this effect is associated with an increase in the amplitude of the anomalous component of the Hall resistance rhoH (the amplitude increases by more than five orders of magnitude with decreasing temperature in the range 1.8-20 K). The emergence of the anomalous contribution to rho(H) is attributed to the transition from the spin-polaron to coherent regime of electron density fluctuations in the vicinity of Fe centers and to the formation of nanosize ferromagnetic regions, i.e., ferrons (about 10 Angstrom in diameter), in the FeSi matrix at T < T-C = 15 K. An additional contribution to the Hall effect, which is observed near the temperature of sign reversal of &rho;(H) and is manifested as the second harmonic in the angular dependences &rho;(H)(&phi;), cannot be explained in the framework of traditional phenomenological models. Analysis of magnetoresistance of FeSi in the spin-polaron and coherent spin fluctuation modes shows that the sign reversal of the ratio &UDelta;&rho;(H)/&rho; accompanied by a transition from a positive (&UDelta;&rho;/&rho; > 0, T > T-m) to a negative (Deltarho/rho < 0, T < T-m) magnetoresistance is observed in the immediate vicinity of the mictomagnetic phase boundary at T-m = 7 K. The linear asymptotic form of the negative magnetoresistance Deltarho/rho proportional to-H in weak magnetic fields up to 10 kOe is explained by the formation of magnetic nanoclusters from interacting ferrons in the mictomagnetic phase of FeSi at T < T-m. The results are used for constructing for the first time the low-temperature magnetic phase diagram of FeSi. The effects of exchange enhancement are estimated quantitatively and the effective parameters characterizing the electron subsystem in the paramagnetic (T > TC), ferromagnetic (T-m < T < T-C), and mictomagnetic (T < T-m) phases are determined. Analysis of anomalies in the aggregate of transport, magnetic, and magnetooptical characteristics observed in the vicinity of H-m &AP; 35 kOe at T < T-m leads to the conclusion that a new collinear magnetic phase with M parallel to H exists on the low-temperature phase diagram of iron monosilicide. (C) 2004 MAIK "Nauka/Interperiodica".
ISSN: 1063-7761
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Solid State Physics and Magnetism Section
× corresponding author
# (joint) last author

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