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Magnetic and transport properties of epitaxial thin film MgFe2O4 grown on MgO (100) by molecular beam epitaxy.

Wu HC, Mauit O, Coileáin CÓ, Syrlybekov A, Khalid A, Mouti A, Abid M, Zhang HZ, Abid M, Shvets IV - Sci Rep (2014)

Bottom Line: The presence of APBs was confirmed by transmission electron microscopy.Moreover, post annealing decreases the resistance and enhances the MR of the film, suggesting migration of the APBs.Our results may be valuable for the application of MgFe2O4 in spintronics.

View Article: PubMed Central - PubMed

Affiliation: 1] School of Physics, Beijing Institute of Technology, Beijing, 100081, P. R. China [2] KSU-Aramco Center, King Saud University, Riyadh 11451, Saudi Arabia.

ABSTRACT
Magnesium ferrite is a very important magnetic material due to its interesting magnetic and electrical properties and its chemical and thermal stability. Here we report on the magnetic and transport properties of epitaxial MgFe2O4 thin films grown on MgO (001) by molecular beam epitaxy. The structural properties and chemical composition of the MgFe2O4 films were characterized by X-Ray diffraction and X-Ray photoelectron spectroscopy, respectively. The nonsaturation of the magnetization in high magnetic fields observed for M (H) measurements and the linear negative magnetoresistance (MR) curves indicate the presence of anti-phase boundaries (APBs) in MgFe2O4. The presence of APBs was confirmed by transmission electron microscopy. Moreover, post annealing decreases the resistance and enhances the MR of the film, suggesting migration of the APBs. Our results may be valuable for the application of MgFe2O4 in spintronics.

No MeSH data available.


(a) MR curves for a 114 nm thick MgFe2O4 film after annealing with oxygen for 3 hours, measured at different temperatures. The magnetic field is applied in the film plane along the [100] direction. Inset: Schematic drawing of the setup used to measure the MR. (b) MR ratio as a function of temperature under a field of 2T. Inset: Schematic drawing of spin structure disturbance due to an AF-APB with and without an in-plane external field.
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f3: (a) MR curves for a 114 nm thick MgFe2O4 film after annealing with oxygen for 3 hours, measured at different temperatures. The magnetic field is applied in the film plane along the [100] direction. Inset: Schematic drawing of the setup used to measure the MR. (b) MR ratio as a function of temperature under a field of 2T. Inset: Schematic drawing of spin structure disturbance due to an AF-APB with and without an in-plane external field.

Mentions: The magnetic properties of the MgFe2O4 thin films were investigated by means of a PPMS (Quantum Design). Temperature dependent M (H) loops of a 114 nm thick MgFe2O4 thin film are displayed in Fig. 2a. The external magnetic field is applied in the film plane along [100] direction. It is clear that the film is ferromagnetic in nature at all the temperatures. The coercivity increases with decreasing temperature. The measured magnetization at 300 K and at 1 T is around 115 emu/cm3, which is larger than the value reported for MgFe2O4 nano pillars9 but smaller than the value for MgFe2O4 grown on sapphire substrates11. Interestingly, the magnetization does not saturate in a field of 1T for all temperatures. Figure 2b shows M (H) loops for the same 114 nm thick MgFe2O4 thin film measured at room temperature with the external magnetic field applied along [100] and [110] directions. A significant difference between the M (H) loops for the two field directions is clearly observed. At room temperature, for a 114 nm thick MgFe2O4 thin film, with the field along the [100] direction, the coercivity field is 127 Oe. While when the field is along the [110] direction, the coercivity field increases to 216 Oe. Moreover, the M (H) loop for the field along [110] is much squarer than for field applied along [100]. It is clear that the easy axis, for the films grown, is along the [110] direction and hard axis is along the [100] direction. Figure 3a shows the magnetoresistance curves of a 114 nm thick MgFe2O4 thin film on a MgO substrate measured at different temperatures, where MR is defined as MR = R(H)/R(0)-1. The transport properties of MgFe2O4 were measured using the conventional four-probe method in the PPMS (Inset of Fig. 3a). A bias current of 4 µA was applied between the two outer contact electrodes along the [100] direction of the MgO substrate and a Keithley 2400 was used to measure the voltage drop. The external field was applied along the current direction. From Figure 3a, one can clearly see that the resistance shows a linear response to the external field at all temperatures. The MR ratio as a function of temperature is summarized in Figure 3b. It should be noted that the MR ratio increases with decreasing temperature. A MR ratio of −0.55% was obtained at room temperature and a MR of −3% was achieved at 80K. We would like to mention here that the shape of the MR curves is independent of temperature.


Magnetic and transport properties of epitaxial thin film MgFe2O4 grown on MgO (100) by molecular beam epitaxy.

Wu HC, Mauit O, Coileáin CÓ, Syrlybekov A, Khalid A, Mouti A, Abid M, Zhang HZ, Abid M, Shvets IV - Sci Rep (2014)

(a) MR curves for a 114 nm thick MgFe2O4 film after annealing with oxygen for 3 hours, measured at different temperatures. The magnetic field is applied in the film plane along the [100] direction. Inset: Schematic drawing of the setup used to measure the MR. (b) MR ratio as a function of temperature under a field of 2T. Inset: Schematic drawing of spin structure disturbance due to an AF-APB with and without an in-plane external field.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4228329&req=5

f3: (a) MR curves for a 114 nm thick MgFe2O4 film after annealing with oxygen for 3 hours, measured at different temperatures. The magnetic field is applied in the film plane along the [100] direction. Inset: Schematic drawing of the setup used to measure the MR. (b) MR ratio as a function of temperature under a field of 2T. Inset: Schematic drawing of spin structure disturbance due to an AF-APB with and without an in-plane external field.
Mentions: The magnetic properties of the MgFe2O4 thin films were investigated by means of a PPMS (Quantum Design). Temperature dependent M (H) loops of a 114 nm thick MgFe2O4 thin film are displayed in Fig. 2a. The external magnetic field is applied in the film plane along [100] direction. It is clear that the film is ferromagnetic in nature at all the temperatures. The coercivity increases with decreasing temperature. The measured magnetization at 300 K and at 1 T is around 115 emu/cm3, which is larger than the value reported for MgFe2O4 nano pillars9 but smaller than the value for MgFe2O4 grown on sapphire substrates11. Interestingly, the magnetization does not saturate in a field of 1T for all temperatures. Figure 2b shows M (H) loops for the same 114 nm thick MgFe2O4 thin film measured at room temperature with the external magnetic field applied along [100] and [110] directions. A significant difference between the M (H) loops for the two field directions is clearly observed. At room temperature, for a 114 nm thick MgFe2O4 thin film, with the field along the [100] direction, the coercivity field is 127 Oe. While when the field is along the [110] direction, the coercivity field increases to 216 Oe. Moreover, the M (H) loop for the field along [110] is much squarer than for field applied along [100]. It is clear that the easy axis, for the films grown, is along the [110] direction and hard axis is along the [100] direction. Figure 3a shows the magnetoresistance curves of a 114 nm thick MgFe2O4 thin film on a MgO substrate measured at different temperatures, where MR is defined as MR = R(H)/R(0)-1. The transport properties of MgFe2O4 were measured using the conventional four-probe method in the PPMS (Inset of Fig. 3a). A bias current of 4 µA was applied between the two outer contact electrodes along the [100] direction of the MgO substrate and a Keithley 2400 was used to measure the voltage drop. The external field was applied along the current direction. From Figure 3a, one can clearly see that the resistance shows a linear response to the external field at all temperatures. The MR ratio as a function of temperature is summarized in Figure 3b. It should be noted that the MR ratio increases with decreasing temperature. A MR ratio of −0.55% was obtained at room temperature and a MR of −3% was achieved at 80K. We would like to mention here that the shape of the MR curves is independent of temperature.

Bottom Line: The presence of APBs was confirmed by transmission electron microscopy.Moreover, post annealing decreases the resistance and enhances the MR of the film, suggesting migration of the APBs.Our results may be valuable for the application of MgFe2O4 in spintronics.

View Article: PubMed Central - PubMed

Affiliation: 1] School of Physics, Beijing Institute of Technology, Beijing, 100081, P. R. China [2] KSU-Aramco Center, King Saud University, Riyadh 11451, Saudi Arabia.

ABSTRACT
Magnesium ferrite is a very important magnetic material due to its interesting magnetic and electrical properties and its chemical and thermal stability. Here we report on the magnetic and transport properties of epitaxial MgFe2O4 thin films grown on MgO (001) by molecular beam epitaxy. The structural properties and chemical composition of the MgFe2O4 films were characterized by X-Ray diffraction and X-Ray photoelectron spectroscopy, respectively. The nonsaturation of the magnetization in high magnetic fields observed for M (H) measurements and the linear negative magnetoresistance (MR) curves indicate the presence of anti-phase boundaries (APBs) in MgFe2O4. The presence of APBs was confirmed by transmission electron microscopy. Moreover, post annealing decreases the resistance and enhances the MR of the film, suggesting migration of the APBs. Our results may be valuable for the application of MgFe2O4 in spintronics.

No MeSH data available.