Magnetic Force Microscopy Research Papers (original) (raw)

The interaction of the highly energetic pulsed excimer laser beam with a target material induces non-equilibrium physico-chemical processes which could be harnessed to synthesize a variety of novel and technologically attractive materials... more

The interaction of the highly energetic pulsed excimer laser beam with a target material induces non-equilibrium physico-chemical processes which could be harnessed to synthesize a variety of novel and technologically attractive materials that are difficult to grow using more conventional thin film deposition techniques. In this paper, recent advances on two excimer laser based techniques that we have used in the processing of thin films and surfaces will be presented. First, we demonstrate the synthesis, by Pulsed Laser Melting (PLM), of silicon supersaturated with sulfur at concentrations several orders of magnitude greater than the solubility limit of silicon alloys, with strong sub-bandgap optical absorption. This material has potential applications in the fabrication of Si-based opto-electronic devices. Second, the capability of Remote Plasma Pulsed Laser Deposition (RP-PLD) in synthesizing the meta-stable half-metallic CrO II compound that is of great interest in the field of spintronics was assessed. Infra-Red spectroscopy and Magnetic Force Microscopy indicate that the use of the remote plasma is beneficial to the formation of the CrO II phase, at a deposition pressure of 30 mTorr and for deposition temperature below 350 °C. Atomic Force Microscopy and Magnetic Force Microscopy studies respectively show that films containing the CrO II phase have significantly different surface topography and magnetic characteristics from those in which the Cr IIO 3 phase is dominant.

Thin polycrystalline films of permalloy (Ni79Fe21) and permendur (Co50Fe50) have been irradiated with Xe-ions to fluences of 1014–1016 ions/cm2. Ion-induced structural and magnetic modifications have been measured by grazing angle X-ray... more

Thin polycrystalline films of permalloy (Ni79Fe21) and permendur (Co50Fe50) have been irradiated with Xe-ions to fluences of 1014–1016 ions/cm2. Ion-induced structural and magnetic modifications have been measured by grazing angle X-ray diffraction, Rutherford backscattering and magneto-optical Kerr effect. In the case of permendur, the Xe-ion implantation first reduced the coercivity, because of stress relaxation, while higher ion fluences increased the coercivity due to pinning centers generated in the film. The ion irradiation aligned the in-plane easy axis of the magnetization along the direction of the external magnetic field during implantation. Phase shifts obtained from magnetic force microscopy confirmed these modifications. The effects of Xe-ion irradiation in permalloy films are much weaker and underline the importance of magnetostriction in the variation of the coercivity and anisotropy.

We report on the high-pressure pulsed laser deposition growth of zinc oxide nanowires containing about 0.2 at.% Co and 0.5 at.% Mn by NiO and Au catalyst. Scanning electron microscopy and X-ray diffraction measurements revealed arrays of... more

We report on the high-pressure pulsed laser deposition growth of zinc oxide nanowires containing about 0.2 at.% Co and 0.5 at.% Mn by NiO and Au catalyst. Scanning electron microscopy and X-ray diffraction measurements revealed arrays of parallel-standing nanowires with hexagonal cross section and uniform in-plane epitaxial relations without rotational domains. Elemental analysis was carried out using particle induced X-ray emission and Q-band electron spin resonance. The valence of the incorporated Mn was determined to be 2+. Atomic and magnetic force microscopy measurements indicate that Mn is incorporated preferentially at the nanowire boundaries.

A generalized model to recover the magnetic permeability μ of linear magnetic medium thin films from magnetic force microscopy (MFM), data under magnetostatic conditions is developed. In the mathematical treatment, where no assumption is... more

A generalized model to recover the magnetic permeability μ of linear magnetic medium thin films from magnetic force microscopy (MFM), data under magnetostatic conditions is developed. In the mathematical treatment, where no assumption is made about the symmetry of the stray field, shape or magnetization for the MFM tip, we are lead to an inverse problem by entailing a nonlinear system of equations and obtain from the experimental data both physical magnitudes wanted: the thickness of the film bμ and μ. On the other hand, relations between superconducting and magnetic thin films are obtained, solving the problem of calibration functions and allowing to recover for a superconducting material the London penetration depth λ as well as the film thickness bλ.

Thin polycrystalline films of permalloy (Ni79Fe21) and permendur (Co50Fe50) have been irradiated with Xe-ions to fluences of 1014−1016 ions/cm2. Ion-induced structural and magnetic modifications have been measured by grazing angle X-ray... more

Thin polycrystalline films of permalloy (Ni79Fe21) and permendur (Co50Fe50) have been irradiated with Xe-ions to fluences of 1014−1016 ions/cm2. Ion-induced structural and magnetic modifications have been measured by grazing angle X-ray diffraction, Rutherford backscattering and magneto-optical Kerr effect. In the case of permendur, the Xe-ion implantation first reduced the coercivity, because of stress relaxation, while higher ion fluences increased the coercivity due to pinning centers generated in the film. The ion irradiation aligned the in-plane easy axis of the magnetization along the direction of the external magnetic field during implantation. Phase shifts obtained from magnetic force microscopy confirmed these modifications. The effects of Xe-ion irradiation in permalloy films are much weaker and underline the importance of magnetostriction in the variation of the coercivity and anisotropy.

The microstructures of composite xBaTiO 3 –(1−x)(Ni 0.5 Zn 0.5 )Fe 2 O 4 (BT–NZF) multiferroics with various mixing ratios (x = 0.50, 0.60 and 0.70) are investigated by means of electron backscatter diffraction (EBSD) and magnetic force... more

The microstructures of composite xBaTiO 3 –(1−x)(Ni 0.5 Zn 0.5 )Fe 2 O 4 (BT–NZF) multiferroics with various mixing ratios (x = 0.50, 0.60 and 0.70) are investigated by means of electron backscatter diffraction (EBSD) and magnetic force microscopy (MFM). The EBSD measurements ...

The paper presents magnetic force microscopy (MFM) studies on the effect of crystallographic orientation and external magnetic field on magnetic microstructure in a bulk polycrystalline iron specimen. The mag-neto crystalline anisotropic... more

The paper presents magnetic force microscopy (MFM) studies on the effect of crystallographic orientation and external magnetic field on magnetic microstructure in a bulk polycrystalline iron specimen. The mag-neto crystalline anisotropic effect on the domain structure is characterized with the support of electron backscatter diffraction study. The distinct variations in magnetic domain structure are observed based on the crystallographic orientation of the grain surface normal with respect to the cube axis i.e. the easy axis of magnetization. Further, the local magnetization behavior is studied in-situ by MFM in presence of external magnetic field in the range of À2000 to 2000 Oe. Various micro-magnetization phenomena such as reversible and irreversible domain wall movements, expansion and contraction of domains, Barkhausen jump, bowing of a pinned domain wall and nucleation of a spike domain are visualized. The respective changes in the magnetic microstructure are compared with the bulk magnetization obtained using vibrating sample magnetometer. Bowing of a domain wall, pinned at two points, upon application of magnetic field is used to estimate the domain wall energy density. The MFM studies in presence of external field applied in two perpendicular directions are used to reveal the influence of the crystalline anisotropy on the local micro-magnetization.

We present a comprehensive study of the magnetic and microwave properties of piezoelectric BaTiO3/magnetostrictive Ni nanocomposites (NCs), fabricated under uniaxial compression, at room temperature. In the current work, we investigated... more

We present a comprehensive study of the magnetic and microwave properties of piezoelectric BaTiO3/magnetostrictive Ni nanocomposites (NCs), fabricated under uniaxial compression, at room temperature. In the current work, we investigated samples in the compositional range between 0≤fNi≤33.5 vol % and from 0.1 to 6 GHz using broadband microwave spectroscopy in combination with atomic and magnetic force microscopy (MFM), x-ray diffraction (XRD), electron transport, and broadband (6-28 GHz) ferromagnetic resonance (FMR) experiments in the microwave regime to correlate magnetization dynamics, electromagnetic materials parameters, and microstructural information. The static magnetic response is consistent with a model of a composite medium with an unmodified Ni phase in a nonmagnetic matrix. We provide the experimental evidence for a magnetoelectric (ME) effect, i.e., the effective permittivity at microwave frequencies can be controlled by an external magnetic field, which makes these nanostructures ready for microwave tunable devices, sensors, and transducers. We show in the analysis that this magnetic field dependence is inconsistent with expectations from magnetoresistance and magnetocapacitance effects, and propose as an alternative an explanation based on the striction across the interfaces between the magnetic and piezoelectric phases. By varying the Ni content and frequency, room temperature broadband FMR was performed in order to investigate the different contributions, e.g., inhomogeneous broadening, to the effective linewidth and microwave damping. The line broadening and asymmetry of the FMR features are not intrinsic properties of the metallic nanophase but reflects the local nonmagnetic environment in which they are embedded. The increase in the effective Gilbert damping coefficient as function of the Ni content is related to the strong increase in the damping experienced by the precessing magnetization in the Ni phase. One of the characteristic features of the present results is the significant correlation between the internal field probed by FMR and the ME coupling coefficient evaluated by microwave spectroscopy which was not observed in our previous study of ZnO/Ni NCs. The present results highlight the strong influence of interfaces of the composite constituent play a crucial role in the analysis of the ME coupling. In addition MFM has been successfully used to detect the strong magnetic contrast between the phases of these nanostructures which indicates local changes in composition and structure.

The multiferroic behavior of epitaxial γ-Fe 2O 3-BiFeO 3 (composite)/Bi 3.25La 0.75Ti 3O 12 bi-layered heterostructures grown on SrRuO 3/SrTiO 3 (1 1 1) substrates has been studied using piezoresponse force microscopy, magnetic force... more

The multiferroic behavior of epitaxial γ-Fe 2O 3-BiFeO 3 (composite)/Bi 3.25La 0.75Ti 3O 12 bi-layered heterostructures grown on SrRuO 3/SrTiO 3 (1 1 1) substrates has been studied using piezoresponse force microscopy, magnetic force microscopy and magnetometry. The ferroelectric domain structure is ascribed to the BiFeO 3 phase while the magnetism originates in the γ-Fe 2O 3 phase of the composite layer. Our studies demonstrate the presence and switching of magnetic and ferroelectric domains within the same area of the sample. This confirms the presence of multiferroic behavior at the nanoscale in our γ-Fe 2O 3-BiFeO 3 nanocomposite thin films.