Limits...
Possible magnetic-polaron-switched positive and negative magnetoresistance in the GdSi single crystals.

Li H, Xiao Y, Schmitz B, Persson J, Schmidt W, Meuffels P, Roth G, Brückel T - Sci Rep (2012)

Bottom Line: Around T(N) the PMRV translates to negative, down to ~-10.5%.Their theory-breaking magnetic-field dependencies [PMRV: dominantly linear; negative MR value (NMRV): quadratic] and the unusual NTVE indicate that PMRV is induced by the formation of magnetic polarons in 5d bands, whereas NMRV is possibly due to abated electron-spin scattering resulting from magnetic-field-aligned local 4f spins.Our results may open up a new avenue of searching for giant MR materials by suppressing the AFM transition temperature, opposite the case in manganites, and provide a promising approach to novel magnetic and electric devices.

View Article: PubMed Central - PubMed

Affiliation: Jülich Centre for Neutron Science JCNS, Forschungszentrum Jülich GmbH, Outstation at Institut Laue-Langevin, Boîte Postale 156, F-38042 Grenoble Cedex 9, France. h.li@fz-juelich.de

ABSTRACT
Magnetoresistance (MR) has attracted tremendous attention for possible technological applications. Understanding the role of magnetism in manipulating MR may in turn steer the searching for new applicable MR materials. Here we show that antiferromagnetic (AFM) GdSi metal displays an anisotropic positive MR value (PMRV), up to ~415%, accompanied by a large negative thermal volume expansion (NTVE). Around T(N) the PMRV translates to negative, down to ~-10.5%. Their theory-breaking magnetic-field dependencies [PMRV: dominantly linear; negative MR value (NMRV): quadratic] and the unusual NTVE indicate that PMRV is induced by the formation of magnetic polarons in 5d bands, whereas NMRV is possibly due to abated electron-spin scattering resulting from magnetic-field-aligned local 4f spins. Our results may open up a new avenue of searching for giant MR materials by suppressing the AFM transition temperature, opposite the case in manganites, and provide a promising approach to novel magnetic and electric devices.

No MeSH data available.


Related in: MedlinePlus

Temperature-dependent structural parameters.(a) Anisotropic character of the lattice-constants, a, b and c, variation. (b) Anomalous unit-cell volume, V, expansion with temperature in the Pnma symmetry. The solid lines are theoretical estimates of the temperature-dependent structural parameters using the Grüneisen model with Debye temperature of θD = 340 K, which is the same as reported in Ref. [10]. Upon warming, two appreciable anomalies display in the structural parameters at respective temperatures of TN1 ≈ 54.3 K (at 0.06 T) and T1 ≈ 100 K. Error bars in (a) and (b) are the standard deviation obtained from the Fullprof refinements.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3475993&req=5

f1: Temperature-dependent structural parameters.(a) Anisotropic character of the lattice-constants, a, b and c, variation. (b) Anomalous unit-cell volume, V, expansion with temperature in the Pnma symmetry. The solid lines are theoretical estimates of the temperature-dependent structural parameters using the Grüneisen model with Debye temperature of θD = 340 K, which is the same as reported in Ref. [10]. Upon warming, two appreciable anomalies display in the structural parameters at respective temperatures of TN1 ≈ 54.3 K (at 0.06 T) and T1 ≈ 100 K. Error bars in (a) and (b) are the standard deviation obtained from the Fullprof refinements.

Mentions: The x-ray powder diffraction analysis (Fig. 1) clearly shows three distinct structural regimes (I, II and III). Upon cooling, the refined (Re) a, b, c and V shrink almost linearly before T1, followed by a slower decrease until sharp turns at TN1, an onset temperature of the AFM transition. Below TN1, the increases of a and b and the decrease of c ultimately result in an unusual NTVE (i.e., PMV) in the unit-cell volume V, which is quite useful in fabricating applicable materials with controlled thermal expansion values1314. Obviously broadening in the nuclear Bragg peaks is present in the I regime (see Supplementary Fig. S1b), which is attributed to the magnetoelastic effect (the coupling between magnetic moments and lattice strains). The strain distribution patterns are extracted and shown in Supplementary Fig. S2. The variations in a, b, c and V below TN1 imply that magnetic anisotropy (MA) (which is consistent with Supplementary Fig. S3a and uncommon for the S-state Gd-compounds), spontaneous PMV and anisotropic MS effects exist in GdSi.


Possible magnetic-polaron-switched positive and negative magnetoresistance in the GdSi single crystals.

Li H, Xiao Y, Schmitz B, Persson J, Schmidt W, Meuffels P, Roth G, Brückel T - Sci Rep (2012)

Temperature-dependent structural parameters.(a) Anisotropic character of the lattice-constants, a, b and c, variation. (b) Anomalous unit-cell volume, V, expansion with temperature in the Pnma symmetry. The solid lines are theoretical estimates of the temperature-dependent structural parameters using the Grüneisen model with Debye temperature of θD = 340 K, which is the same as reported in Ref. [10]. Upon warming, two appreciable anomalies display in the structural parameters at respective temperatures of TN1 ≈ 54.3 K (at 0.06 T) and T1 ≈ 100 K. Error bars in (a) and (b) are the standard deviation obtained from the Fullprof refinements.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3475993&req=5

f1: Temperature-dependent structural parameters.(a) Anisotropic character of the lattice-constants, a, b and c, variation. (b) Anomalous unit-cell volume, V, expansion with temperature in the Pnma symmetry. The solid lines are theoretical estimates of the temperature-dependent structural parameters using the Grüneisen model with Debye temperature of θD = 340 K, which is the same as reported in Ref. [10]. Upon warming, two appreciable anomalies display in the structural parameters at respective temperatures of TN1 ≈ 54.3 K (at 0.06 T) and T1 ≈ 100 K. Error bars in (a) and (b) are the standard deviation obtained from the Fullprof refinements.
Mentions: The x-ray powder diffraction analysis (Fig. 1) clearly shows three distinct structural regimes (I, II and III). Upon cooling, the refined (Re) a, b, c and V shrink almost linearly before T1, followed by a slower decrease until sharp turns at TN1, an onset temperature of the AFM transition. Below TN1, the increases of a and b and the decrease of c ultimately result in an unusual NTVE (i.e., PMV) in the unit-cell volume V, which is quite useful in fabricating applicable materials with controlled thermal expansion values1314. Obviously broadening in the nuclear Bragg peaks is present in the I regime (see Supplementary Fig. S1b), which is attributed to the magnetoelastic effect (the coupling between magnetic moments and lattice strains). The strain distribution patterns are extracted and shown in Supplementary Fig. S2. The variations in a, b, c and V below TN1 imply that magnetic anisotropy (MA) (which is consistent with Supplementary Fig. S3a and uncommon for the S-state Gd-compounds), spontaneous PMV and anisotropic MS effects exist in GdSi.

Bottom Line: Around T(N) the PMRV translates to negative, down to ~-10.5%.Their theory-breaking magnetic-field dependencies [PMRV: dominantly linear; negative MR value (NMRV): quadratic] and the unusual NTVE indicate that PMRV is induced by the formation of magnetic polarons in 5d bands, whereas NMRV is possibly due to abated electron-spin scattering resulting from magnetic-field-aligned local 4f spins.Our results may open up a new avenue of searching for giant MR materials by suppressing the AFM transition temperature, opposite the case in manganites, and provide a promising approach to novel magnetic and electric devices.

View Article: PubMed Central - PubMed

Affiliation: Jülich Centre for Neutron Science JCNS, Forschungszentrum Jülich GmbH, Outstation at Institut Laue-Langevin, Boîte Postale 156, F-38042 Grenoble Cedex 9, France. h.li@fz-juelich.de

ABSTRACT
Magnetoresistance (MR) has attracted tremendous attention for possible technological applications. Understanding the role of magnetism in manipulating MR may in turn steer the searching for new applicable MR materials. Here we show that antiferromagnetic (AFM) GdSi metal displays an anisotropic positive MR value (PMRV), up to ~415%, accompanied by a large negative thermal volume expansion (NTVE). Around T(N) the PMRV translates to negative, down to ~-10.5%. Their theory-breaking magnetic-field dependencies [PMRV: dominantly linear; negative MR value (NMRV): quadratic] and the unusual NTVE indicate that PMRV is induced by the formation of magnetic polarons in 5d bands, whereas NMRV is possibly due to abated electron-spin scattering resulting from magnetic-field-aligned local 4f spins. Our results may open up a new avenue of searching for giant MR materials by suppressing the AFM transition temperature, opposite the case in manganites, and provide a promising approach to novel magnetic and electric devices.

No MeSH data available.


Related in: MedlinePlus