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Unveiling hidden ferrimagnetism and giant magnetoelectricity in polar magnet Fe2Mo3O8.

Wang Y, Pascut GL, Gao B, Tyson TA, Haule K, Kiryukhin V, Cheong SW - Sci Rep (2015)

Bottom Line: Magnetoelectric (ME) effect is recognized for its utility for low-power electronic devices.Largest ME coefficients are often associated with phase transitions in which ferroelectricity is induced by magnetic order.The observed effects are associated with a hidden ferrimagnetic order unveiled by application of a magnetic field.

View Article: PubMed Central - PubMed

Affiliation: Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.

ABSTRACT
Magnetoelectric (ME) effect is recognized for its utility for low-power electronic devices. Largest ME coefficients are often associated with phase transitions in which ferroelectricity is induced by magnetic order. Unfortunately, in these systems, large ME response is revealed only upon elaborate poling procedures. These procedures may become unnecessary in single-polar-domain crystals of polar magnets. Here we report giant ME effects in a polar magnet Fe2Mo3O8 at temperatures as high as 60 K. Polarization jumps of 0.3 μC/cm(2), and repeated mutual control of ferroelectric and magnetic moments with differential ME coefficients on the order of 10(4) ps/m are achieved. Importantly, no electric or magnetic poling is needed, as necessary for applications. The sign of the ME coefficients can be switched by changing the applied "bias" magnetic field. The observed effects are associated with a hidden ferrimagnetic order unveiled by application of a magnetic field.

No MeSH data available.


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Magnetic transition in Fe2Mo3O8.(a) Crystal structure of Fe2Mo3O8. Vertical lines connect the nearest Fe ions along the c axis (blue lines are longer than the red ones). (b) The Fe-O layer in the ab crystallographic plane. Thick line depicts the largest Fe-Fe magnetic coupling J. (c) Schematic view of the AFM and FRM orders. Pink arrows represent the ferrimagnetic moments of the individual Fe-O layers. (d) The AFM order, together with the calculated largest ionic shifts associated with the paramagnetic to AFM transition. The direction of the magnetically-induced ΔP is shown with a thick arrow. (e) Temperature dependence of DC magnetic susceptibility χDC in zero field-cooled (ZFC) and field-cooled (FC) processes along two crystallographic directions, parallel and perpendicular to the c axis, in μ0H = 0.2 T. (f) Specific heat anomaly at the Neel temperature. Red line represents the double Debye model fit discussed in the text. Insert: the image of as-grown Fe2Mo3O8 single crystal.
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f1: Magnetic transition in Fe2Mo3O8.(a) Crystal structure of Fe2Mo3O8. Vertical lines connect the nearest Fe ions along the c axis (blue lines are longer than the red ones). (b) The Fe-O layer in the ab crystallographic plane. Thick line depicts the largest Fe-Fe magnetic coupling J. (c) Schematic view of the AFM and FRM orders. Pink arrows represent the ferrimagnetic moments of the individual Fe-O layers. (d) The AFM order, together with the calculated largest ionic shifts associated with the paramagnetic to AFM transition. The direction of the magnetically-induced ΔP is shown with a thick arrow. (e) Temperature dependence of DC magnetic susceptibility χDC in zero field-cooled (ZFC) and field-cooled (FC) processes along two crystallographic directions, parallel and perpendicular to the c axis, in μ0H = 0.2 T. (f) Specific heat anomaly at the Neel temperature. Red line represents the double Debye model fit discussed in the text. Insert: the image of as-grown Fe2Mo3O8 single crystal.

Mentions: Fe2Mo3O8, known as the mineral kamiokite3031, consists of honeycomb-like Fe-O layers separated by sheets of Mo4+ ions, See Fig. 1(a). The layers are stacked along the c axis. The Fe-O layer is formed in the ab plane by corner-sharing FeO4 tetrahedra and FeO6 octahedra, as shown in Fig. 1(b). In this layer, the tetrahedral (Fet) and octahedral (FeO) triangular sublattices are shifted along the c axis by 0.614 Å with respect to each other31, leading to short and long interlayer Fe-Fe distances, see Fig. 1(a). The vertices of the FeO4 tetrahedra point along the positive c axis, reflecting the polar structure of Fe2Mo3O8 (ref. 31). The Mo kagome-like layer is trimerized. The Mo trimers are in the singlet state, and do not contribute to magnetism32. Below TN ≈ 60 K, the Fe2+ moments exhibit the antiferromagnetic (AFM) order in the honeycomb layers, see Fig. 1(c). As discussed below, FeO has larger spin than Fet, and therefore each of the Fe-O layers is ferrimagnetic33. Along the c axis, the nearest Fe spins are aligned in the same direction, implying ferromagnetic interlayer coupling. The resulting stacking of the ferrimagnetic Fe-O layers along the c axis leads to vanishing macroscopic magnetic moment, and we call this state AFM.


Unveiling hidden ferrimagnetism and giant magnetoelectricity in polar magnet Fe2Mo3O8.

Wang Y, Pascut GL, Gao B, Tyson TA, Haule K, Kiryukhin V, Cheong SW - Sci Rep (2015)

Magnetic transition in Fe2Mo3O8.(a) Crystal structure of Fe2Mo3O8. Vertical lines connect the nearest Fe ions along the c axis (blue lines are longer than the red ones). (b) The Fe-O layer in the ab crystallographic plane. Thick line depicts the largest Fe-Fe magnetic coupling J. (c) Schematic view of the AFM and FRM orders. Pink arrows represent the ferrimagnetic moments of the individual Fe-O layers. (d) The AFM order, together with the calculated largest ionic shifts associated with the paramagnetic to AFM transition. The direction of the magnetically-induced ΔP is shown with a thick arrow. (e) Temperature dependence of DC magnetic susceptibility χDC in zero field-cooled (ZFC) and field-cooled (FC) processes along two crystallographic directions, parallel and perpendicular to the c axis, in μ0H = 0.2 T. (f) Specific heat anomaly at the Neel temperature. Red line represents the double Debye model fit discussed in the text. Insert: the image of as-grown Fe2Mo3O8 single crystal.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4508583&req=5

f1: Magnetic transition in Fe2Mo3O8.(a) Crystal structure of Fe2Mo3O8. Vertical lines connect the nearest Fe ions along the c axis (blue lines are longer than the red ones). (b) The Fe-O layer in the ab crystallographic plane. Thick line depicts the largest Fe-Fe magnetic coupling J. (c) Schematic view of the AFM and FRM orders. Pink arrows represent the ferrimagnetic moments of the individual Fe-O layers. (d) The AFM order, together with the calculated largest ionic shifts associated with the paramagnetic to AFM transition. The direction of the magnetically-induced ΔP is shown with a thick arrow. (e) Temperature dependence of DC magnetic susceptibility χDC in zero field-cooled (ZFC) and field-cooled (FC) processes along two crystallographic directions, parallel and perpendicular to the c axis, in μ0H = 0.2 T. (f) Specific heat anomaly at the Neel temperature. Red line represents the double Debye model fit discussed in the text. Insert: the image of as-grown Fe2Mo3O8 single crystal.
Mentions: Fe2Mo3O8, known as the mineral kamiokite3031, consists of honeycomb-like Fe-O layers separated by sheets of Mo4+ ions, See Fig. 1(a). The layers are stacked along the c axis. The Fe-O layer is formed in the ab plane by corner-sharing FeO4 tetrahedra and FeO6 octahedra, as shown in Fig. 1(b). In this layer, the tetrahedral (Fet) and octahedral (FeO) triangular sublattices are shifted along the c axis by 0.614 Å with respect to each other31, leading to short and long interlayer Fe-Fe distances, see Fig. 1(a). The vertices of the FeO4 tetrahedra point along the positive c axis, reflecting the polar structure of Fe2Mo3O8 (ref. 31). The Mo kagome-like layer is trimerized. The Mo trimers are in the singlet state, and do not contribute to magnetism32. Below TN ≈ 60 K, the Fe2+ moments exhibit the antiferromagnetic (AFM) order in the honeycomb layers, see Fig. 1(c). As discussed below, FeO has larger spin than Fet, and therefore each of the Fe-O layers is ferrimagnetic33. Along the c axis, the nearest Fe spins are aligned in the same direction, implying ferromagnetic interlayer coupling. The resulting stacking of the ferrimagnetic Fe-O layers along the c axis leads to vanishing macroscopic magnetic moment, and we call this state AFM.

Bottom Line: Magnetoelectric (ME) effect is recognized for its utility for low-power electronic devices.Largest ME coefficients are often associated with phase transitions in which ferroelectricity is induced by magnetic order.The observed effects are associated with a hidden ferrimagnetic order unveiled by application of a magnetic field.

View Article: PubMed Central - PubMed

Affiliation: Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.

ABSTRACT
Magnetoelectric (ME) effect is recognized for its utility for low-power electronic devices. Largest ME coefficients are often associated with phase transitions in which ferroelectricity is induced by magnetic order. Unfortunately, in these systems, large ME response is revealed only upon elaborate poling procedures. These procedures may become unnecessary in single-polar-domain crystals of polar magnets. Here we report giant ME effects in a polar magnet Fe2Mo3O8 at temperatures as high as 60 K. Polarization jumps of 0.3 μC/cm(2), and repeated mutual control of ferroelectric and magnetic moments with differential ME coefficients on the order of 10(4) ps/m are achieved. Importantly, no electric or magnetic poling is needed, as necessary for applications. The sign of the ME coefficients can be switched by changing the applied "bias" magnetic field. The observed effects are associated with a hidden ferrimagnetic order unveiled by application of a magnetic field.

No MeSH data available.


Related in: MedlinePlus