E. Nazaretski

Design of a variable temperature scanning force microscope.

We have developed the variable temperature scanning force microscope capable of performing both magnetic resonance force microscopy (MRFM) and magnetic force microscopy (MFM) measurements in the temperature range between 5 and 300 K. Modular design, large scanning area, and interferometric detection of the cantilever deflection make it a sensitive, easy to operate, and reliable instrument suitable for studies of the dynamic and static magnetization in various systems. We have verified the performance of the microscope by imaging vortices in a Nb thin film in the MFM mode of operation. MRFM spectra in a diphenyl-picryl-hydrazyl film were recorded to evaluate the MRFM mode of operation.

Ferromagnetic resonance force microscopy on a thin permalloy film

Ferromagnetic resonance force microscopy (FMRFM) offers a means of performing local ferromagnetic resonance. The authors have studied the evolution of the FMRFM force spectra in a continuous 50nm thick permalloy film as a function of probe-film distance and performed numerical simulations of the intensity of the FMRFM probe-film interaction force, accounting for the presence of the localized strongly nonuniform magnetic field of the FMRFM probe magnet. Excellent agreement between the experimental data and the simulation results provides insight into the mechanism of FMR mode excitation in a FMRFM experiment.

Temperature-dependent magnetic resonance force microscopy studies of a thin Permalloy film

We used magnetic resonance force microscopy (MRFM) to study a 50nm thick continuous Permalloy film. We mechanically measured the ferromagnetic resonance signal in the temperature range between 10 and 70K in the presence of a static magnetic field applied normal to the surface of the film. The measurements show a decrease of the ferromagnetic resonance field with increasing temperature. We attribute this behavior to the temperature-dependent changes of the saturation magnetization. Our experiments demonstrate the potential of MRFM to perform quantitative ferromagnetic resonance measurements as a function of temperature.

Assembly and magnetic properties of nickel nanoparticles on silicon nanowires

The directed assembly of magnetic Ni nanoparticles at the tips of silicon nanowires is reported. Using electrodeposition Ni shells of thickness from 10 to 200 nm were selectively deposited on Au catalytic seeds at the ends of nanowires. Magnetic characterization confirms a low coercivity (≈115 Oe) ferromagnetic behavior at 300 K. This approach to multifunctional magnetic-semiconducting nanostructure assembly could be extended to electrodeposition of other materials on the nanowire ends, opening up additional approaches to device integration. Such magnetically functionalized nanowires offer an approach to developing highly localized magnetic probes for high resolution magnetic resonance force microscopy.

Low Temperature Magnetic Resonance Force Microscope: Design and Performance

We describe the design and operation of a cryogenic magnetic resonance force microscope suitable for detecting electron spin and ferromagnetic resonance. Microscope‐critical components are described, including scanning probe stages, cantilever with a micromagnet attached, fiber optic interferometer, and microwave resonator. The performance of the apparatus has been evaluated at 4 K using diphenylpicrylhydrazyl (DPPH) as a reference sample. Our experiments have demonstrated the sensitivity of the microscope to be better than 3×104 electron spins.

Large magnetic penetration depth and thermal fluctuations in a superconducting Ca10(Pt3As8)[(Fe1 xPtx)2As2]5 (x = 0.097) single crystal

We have measured the temperature dependence of the absolute value of the magnetic penetration depth {lambda}(T) in a Ca{sub 10}(Pt{sub 3}As{sub 8})[(Fe{sub 1-x}Pt{sub x}){sub 2}As{sub 2}]{sub 5} (x = 0.097) single crystal using a low-temperature magnetic force microscope (MFM). We obtain {lambda}{sub ab}(0) {approx} 1000 nm via extrapolating the data to T = 0. This large {lambda} and pronounced anisotropy in this system are responsible for large thermal fluctuations and the presence of a liquid vortex phase in this low-temperature superconductor with a critical temperature of 11 K, consistent with the interpretation of the electrical transport data. The superconducting parameters obtained from {lambda} and coherence length {zeta} place this compound in the extreme type II regime. Meissner responses (via MFM) at different locations across the sample are similar to each other, indicating good homogeneity of the superconducting state on a submicron scale.

Measurement of the magnetic penetration depth of a superconducting MgB2 thin film with a large intraband diffusivity

We report the temperature dependent magnetic penetration depth

Detection of localized ferromagnetic resonance in a continuous thin film via magnetic resonance force microscopy

\lambda(T)

Spatial characterization of the magnetic field profile of a probe tip used in magnetic resonance force microscopy

and the superconducting critical field

Effect of localized magnetic field on the uniform ferromagnetic resonance mode in a thin film

H_{c2}(T)