Browsing by Author "Lin, T. H."

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Anomalous magnetic ordering in b-axis-oriented orthorhombic HoMnO(3) thin films
(2008-03-31)
Lin, T. H.
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Hsieh, C. C.
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Shih, H. C.
;
Luo, C. W.
;
Uen, T. M.
Orthorhombic HoMnO(3) films with well-aligned crystallographic orientations were deposited on LaAlO(3)(110) single crystal substrates by using pulsed laser deposition. The nearly perfect b-axis-oriented films provide the opportunity of investigating the orientation-dependent physical property of this material. The temperature dependent magnetization evidently displays an antiferromagnetic ordering near 42 K, irrespective to the direction of applied field. Furthermore, the theoretically expected lock-in transition was clearly observed at around 30 K when field was applied along the c axis and was undetectable along the a and b axes. The 30 K transition was suppressed to 26 K when the applied field increased from 100 to 500 Oe. (C) 2008 American Institute of Physics.
Effects of compressive epitaxial strain in the b-axis on the magnetization response of orthorhombic HoMnO(3) thin films
(2009)
Lin, T. H.
;
Hsieh, C. C.
;
Shih, H. C.
;
Luo, C. W.
;
Uen, T. M.
The orthorhombic phase HoMnO(3) (o-HMO in Pbnm symmetry setting) thin films were prepared on LaAlO(3)(110) (LAO(110)) substrates by pulsed laser deposition. While for films grown on LAO(110) substrates, the compressive strain along the b-axis was resulted from the tensile strain in the a-c plane. The films provide the opportunity of investigating the effects of strain, hence lattice elasticity, on the physical properties of this material. For o-HMO films an antiferromagnetic ordering with T(N)similar to 42 K, irrespective to the direction of applied field was clearly observed. However, an additional magnetic ordering occurring around 26.4 K was observed when the field was applied along the c-axis of o-HMO. This transition, however, was absent when the field was applied along a-and b-axis. These results indicate that the second magnetic ordering observed along the c-axis could be more relevant to the Mn moments lying along the partially strained b direction of the o-HMO which has been theoretically expected to result in incommensurate-commensurate lock-in transition.
Electronic Structure and Magnetic Anisotropies in Orthorhombic Multiferroic YMnO(3) Thin Films
(2009-01-01)
Hsieh, C. C.
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Lin, T. H.
;
Shih, H. C.
;
Lin, J-Y
;
Hsu, C-H
Thermodynamically YMnO(3) (YMO) can only exist with hexagonal structure at ambient conditions. In this study, we demonstrate that the stain between film and substrate can play an important role in forming orthorhombic YMO (o-YMO). o-YMO films with nearly perfect crystallographic orientation alignment were obtained on LaAlO(3)(110) substrates. These films allow us to unambiguously disclose the intrinsic magnetic property and electronic structure anisotropies along different crystallographic orientations. The antiferromagnetic (AFM) phase transition was around 42 K. Moreover, we observed a signature of spin reordering at lower temperatures when the applied field was parallel to the a- or c-axis. On the other hand, only the AFM transition was observed when the field is parallel to the b-axis. By comparing the X-ray absorption spectroscopy (XAS) results to standard manganese oxides, YMnO(3) exhibits the dominant Mn(+3) characteristics as that obtained from the standard Mn(2)O(3) powder. The polarization dependent XAS also revealed anisotropic bonding behavior along each crystalline axis.
Electronic Structure and Magnetic Anisotropies in Orthorhombic Multiferroic YMnO3 Thin Films
(2009-01-01)
Hsieh, C. C.
;
Lin, T. H.
;
Shih, H. C.
;
Lin, J-Y
;
Hsu, C-H
Thermodynamically YMnO3 (YMO) can only exist with hexagonal structure at ambient conditions. In this study, we demonstrate that the stain between film and substrate can play an important role in forming orthorhombic YMO (o-YMO). o-YMO films with nearly perfect crystallographic orientation alignment were obtained on LaAlO3(110) substrates. These films allow us to unambiguously disclose the intrinsic magnetic property and electronic structure anisotropies along different crystallographic orientations. The antiferromagnetic (AFM) phase transition was around 42 K. Moreover, we observed a signature of spin reordering at lower temperatures when the applied field was parallel to the a- or c-axis. On the other hand, only the AFM transition was observed when the field is parallel to the b-axis. By comparing the X-ray absorption spectroscopy (XAS) results to standard manganese oxides, YMnO3 exhibits the dominant Mn+3 characteristics as that obtained from the standard Mn2O3 powder. The polarization dependent XAS also revealed anisotropic bonding behavior along each crystalline axis.
Magnetic ordering anisotropy in epitaxial orthorhombic multiferroic YMnO(3) films
(2008-11-15)
Hsieh, C. C.
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Lin, T. H.
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Shih, H. C.
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Hsu, C. -H.
;
Luo, C. W.
Orthorhombic YMnO(3) thin films with (200), (020), and (001) orientations were, respectively, obtained by pulsed laser deposition on SrTiO(3)(110), LaAlO(3)(110), and SrTiO(3)(001) substrates. The results demonstrate that the strain between film and substrate can serve as an alternative in transforming the thermodynamically stable hexagonal YMnO(3) into the orthorhombic phase, which previously could be obtained with high-pressure high temperature syntheses and epitaxy-stabilized thin film processes. More importantly, these films allow us, for the first time, to unambiguously disclose the intrinsic magnetic property along different crystallographic orientations. Our results show that, although the antiferromagnetic (AFM) ordering remains the same, there is an additional spin reordering transition which is very much dependent on the crystallographic orientation along which the measuring field was applied and on the in-plane crystallographic alignment of the films. Detailed analyses indicate that the origin of the observed second reordering may be due to some strain-induced canted AFM state instead of the incommensurate lock-in transitions conceived previously.
Magnetic ordering anisotropy in epitaxial orthorhombic multiferroic YMnO3 films
(2008-11-15)
Hsieh, C. C.
;
Lin, T. H.
;
Shih, H. C.
;
Hsu, C. -H.
;
Luo, C. W.
Orthorhombic YMnO3 thin films with (200), (020), and (001) orientations were, respectively, obtained by pulsed laser deposition on SrTiO3(110), LaAlO3(110), and SrTiO3(001) substrates. The results demonstrate that the strain between film and substrate can serve as an alternative in transforming the thermodynamically stable hexagonal YMnO3 into the orthorhombic phase, which previously could be obtained with high-pressure high temperature syntheses and epitaxy-stabilized thin film processes. More importantly, these films allow us, for the first time, to unambiguously disclose the intrinsic magnetic property along different crystallographic orientations. Our results show that, although the antiferromagnetic (AFM) ordering remains the same, there is an additional spin reordering transition which is very much dependent on the crystallographic orientation along which the measuring field was applied and on the in-plane crystallographic alignment of the films. Detailed analyses indicate that the origin of the observed second reordering may be due to some strain-induced canted AFM state instead of the incommensurate lock-in transitions conceived previously.
Magnetic transition anisotropies in orthorhombic LuMnO(3) and HoMnO(3) multiferroic thin films
(2010)
Tsai, T. Y.
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Lin, T. H.
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Slowry, S.
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Luo, C. W.
;
Wu, K. H.
We have successfully prepared the b-axis-oriented orthorhombic LuMnO(3) (LuMO) and HoMnO(3) (HMO) thin films by pulsed laser deposition on (110)-LaAlO(3) substrates. The nearly perfect alignment between the film growth orientation and the substrate allows us to study the magnetic transitions along the respective crystal orientation, which has displayed marked anisotropic behaviours. In particular, with the largest ionic size difference between Lu and Ho for the family of RMnO(3) displaying the E-type AFM, the effects of lattice distortion on the magnetic transition are compared.
Magnetism-induced ferroelectric polarization in the c-axis-oriented orthorhombic HoMnO(3) thin films
(2009-11-15)
Lin, T. H.
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Hsieh, C. C.
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Luo, C. W.
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Lin, J. -Y.
;
Sun, C. P.
The magnetism-induced ferroelectricity in the E-type orthorhombic HoMnO(3) (o-HMO) films grown on Nb-doped and undoped SrTiO(3)(001) substrates was studied. The temperature dependent magnetization in these films evidently exhibits an antiferromagnetic ordering around 44 K and an anomalous second magnetic ordering along the c-axis near 35 K. Interestingly, at this anomalous transition temperature, an associated ferroelectric polarization was probed by the P-E hysteresis measurements, indicating the intimated coupling between the ferroelectric response and the reordering of Mn spins, which has never been disclosed previously by dielectric constant measurements. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3260241]
Magnetism-induced ferroelectric polarization in the c-axis-oriented orthorhombic HoMnO3 thin films
(2009-11-15)
Lin, T. H.
;
Hsieh, C. C.
;
Luo, C. W.
;
Lin, J. -Y.
;
Sun, C. P.
The magnetism-induced ferroelectricity in the E-type orthorhombic HoMnO3 (o-HMO) films grown on Nb-doped and undoped SrTiO3(001) substrates was studied. The temperature dependent magnetization in these films evidently exhibits an antiferromagnetic ordering around 44 K and an anomalous second magnetic ordering along the c-axis near 35 K. Interestingly, at this anomalous transition temperature, an associated ferroelectric polarization was probed by the P-E hysteresis measurements, indicating the intimated coupling between the ferroelectric response and the reordering of Mn spins, which has never been disclosed previously by dielectric constant measurements. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3260241]
Magnetization dynamics and the Mn(3+) d-d excitation of hexagonal HoMnO(3) single crystals using wavelength-tunable time-resolved femtosecond spectroscopy
(2009-07-01)
Shih, H. C.
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Lin, T. H.
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Luo, C. W.
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Lin, J. -Y.
;
Uen, T. M.
We analyze the photo-induced carrier and magnetization dynamics in antiferromagnetic (AFM) HoMnO(3) single crystals, delineated by wavelength-dependent femtosecond spectroscopy. The emergence of long-range and short-range magnetic order are unambiguously revealed in association with an abnormal blueshift of Mn(3+) 3d level around the Neacuteel temperature and the slope variation in the temperature-dependent transient reflectivity change (Delta R/R) near the Neacuteel transition, respectively. Furthermore, the disturbance (in ps time scale) of the AFM ordering and its reordering time (in a few 100 ps time scale) are clearly identified in the negative Delta R/R..
Magnetization dynamics and the Mn3+ d-d excitation of hexagonal HoMnO3 single crystals using wavelength-tunable time-resolved femtosecond spectroscopy
(2009-07-01)
Shih, H. C.
;
Lin, T. H.
;
Luo, C. W.
;
Lin, J. -Y.
;
Uen, T. M.
We analyze the photo-induced carrier and magnetization dynamics in antiferromagnetic (AFM) HoMnO3 single crystals, delineated by wavelength-dependent femtosecond spectroscopy. The emergence of long-range and short-range magnetic order are unambiguously revealed in association with an abnormal blueshift of Mn3+ 3d level around the Neacuteel temperature and the slope variation in the temperature-dependent transient reflectivity change (Delta R/R) near the Neacuteel transition, respectively. Furthermore, the disturbance (in ps time scale) of the AFM ordering and its reordering time (in a few 100 ps time scale) are clearly identified in the negative Delta R/R..
Strain-induced effects on antiferromagnetic ordering and magnetocapacitance in orthorhombic HoMnO(3) thin films
(2009-01-14)
Lin, T. H.
;
Shih, H. C.
;
Hsieh, C. C.
;
Luo, C. W.
;
Lin, J-Y
We investigated the magnetic and ferroelectric properties of c-axis oriented orthorhombic phase HoMnO(3) (o-HMO in Pbnm symmetry setting) thin films grown on Nb-doped SrTiO(3)(001) substrates. The o-HMO films exhibit an antiferromagnetic ordering near 42 K, irrespective of the orientation of the applied field. However, an additional magnetic ordering occurring around 35 K was observed when the field was applied along the c-axis of o-HMO, which was absent when the field was applied in the ab-plane. The magnetocapacitance measured along the c-axis showed that although there is evidence of dielectric constant enhancement when the temperature is below 35 K the expected abrupt change in dielectric constant appears at a much lower temperature and reaches maximum around 13.5 K, indicating that the low-temperature c-axis polarization might be related to the ordering of the Ho(3+) moment. The lattice constant analyses using x-ray diffraction and the observation of a slight magnetization hysteresis suggest that the weak second magnetic transition along the c- axis at 35 K might be more relevant to the strain-induced effect on antiferromagnetism.
Strain-induced effects on antiferromagnetic ordering and magnetocapacitance in orthorhombic HoMnO3 thin films
(2009-01-14)
Lin, T. H.
;
Shih, H. C.
;
Hsieh, C. C.
;
Luo, C. W.
;
Lin, J-Y
We investigated the magnetic and ferroelectric properties of c-axis oriented orthorhombic phase HoMnO3 (o-HMO in Pbnm symmetry setting) thin films grown on Nb-doped SrTiO3(001) substrates. The o-HMO films exhibit an antiferromagnetic ordering near 42 K, irrespective of the orientation of the applied field. However, an additional magnetic ordering occurring around 35 K was observed when the field was applied along the c-axis of o-HMO, which was absent when the field was applied in the ab-plane. The magnetocapacitance measured along the c-axis showed that although there is evidence of dielectric constant enhancement when the temperature is below 35 K the expected abrupt change in dielectric constant appears at a much lower temperature and reaches maximum around 13.5 K, indicating that the low-temperature c-axis polarization might be related to the ordering of the Ho3+ moment. The lattice constant analyses using x-ray diffraction and the observation of a slight magnetization hysteresis suggest that the weak second magnetic transition along the c- axis at 35 K might be more relevant to the strain-induced effect on antiferromagnetism.
Ultrafast Dynamics of the Mn d-d Transition on Hexagonal HoMnO(3)
(2009)
Shih, H. C.
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Lin, T. H.
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Hsieh, C. C.
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Lee, J. M.
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Luo, C. W.
The photoinduced changes in reflectivity (Delta R/R) at energies closed to the Mn d-d optical transition of HoMnO(3) single crystal have been systematically measured from 300K to 30 K by time-resolved optical pump-probe spectroscopy. The oscillation induced by the propagation of strain pulse was clearly observed in the Delta R/R signal with various probing wavelength. Moreover, the different relaxation processes of photoexcited carriers with in various wavelengths may be led by the blue shift of Mn(3+) d level.