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The stray field of permalloy (Py) micromagnets has been measured by means of a micrometer-sized Hall magnetometer incorporating a ballistic two-dimensional electron system. In particular, ferromagnetic specimens have been investigated where two micromagnets were separated by a sub-[micro]m gap. The two 20 nm thick Py micromagnets had lateral sizes of 1 x 1 [micro][m.sup.2] and 1 x 2 [micro][m.sup.2]. The separation gaps were 200, 300, and 500 nm. The measured Hall curve, which gives the averaged value of the stray field in the cross junction, is hysteretic and reflects the micromagnetic behavior. Systematic changes, most likely indicating magnetostatic interaction, are observed as a function of the separation gap. We show that bend-resistance measurements performed on the same magnetometer give a higher spatial resolution and, thereby, resolve the reversal processes in greater detail than the Hall measurements. Index Terms--Hall effect devices, magnetic domain, magnetization reversal, magnetoresistance devices, micromagnetic switching.

An industrial pulsed field magnetometer was developed, focusing on industrial needs. The system is to be used for the complete characterizing of permanent magnets in a production-line situation. The purpose is to create a fast, reliable, and accurate magnetometer for quality control but also, in a later step, as a standard measurement method for magnets. Index Terms--Eddy currents, hysteresis, measurement.

The application of a miniature orthogonal fluxgate magnetometer to magnetic domain imaging of coated grain-oriented silicon steels is discussed. The method was useful for clearly imaging the well-defined stripe domains with some spike domains and grain boundaries.

The technique for fabrication of planar Hall sensors from GaAs-AlGaAs heterojunctions used for examining the local stray field at a specific section of a micron-sized magnet is described. The occurrence of the magnetization reversal via a magnetic vortex structure was suggested by the hysteresis loop of an electroplated Ni ring measured at 110 K.

Metallic iron, and iron/platinum alloys nanoparticles are synthesized through chemical assembly and then magnetically characterized. Magnetic characterization is performed using superconducting quantum interference device magnetometry.

We have developed a new technique that simulates the thermal magnetization decay (magnetic viscosity) within bit transitions that have a strong demagnetizing field [H.sub.d] approximately equal to the remanent coercivity of the recording medium. This technique uses a vibrating-sample magnetometer to measure the viscosity while allowing the applied field to decay logarithmically at a rate consistent with the measured magnetization decay. The decaying applied field simulates the decaying [H.sub.d] of a broadening bit transition. The magnetic decay measured using this technique remains logarithmic in time, but is almost a factor of 4 smaller than that measured using a constant applied field. These results imply that the standard viscosity measurement is inappropriate when estimating the amount of thermal broadening due to [H.sub.d] within a transition. We have also developed a model of the magnetization decay in a large decaying [H.sub.d] using a modified Arrhenius-Neel rate equation with a single energy barrier that has explicit dependence on the magnetization. The model predicts logarithmic magnetization decay consistent with that observed experimentally and also indicates that the viscosity measured using this technique may be a measure of the average energy barrier preventing thermal switching. Index Terms - Magnetic viscosity, demagnetizing field, bit transition.

Flux patterns in multifilamentary Ag-sheathed (Pb,Bi)(sub2)Sr(sub2)Ca(sub2)Cu(sub3)O(sub10+delta) tapes consisting of 19 filaments, have been visualized by magneto-optic imaging. Shielding current flow mainly in the outer filaments in low fields, but inner filaments also contribute to current flow when the external magnetic field is increased. Magnetization loops were measured by a SQUID magnetometer, and it was revealed that the show the anomalous position of the central peak.

A multichannel high-resolution superconducting quantum interference device magnetomer has been developed to measure biomagnetic fields produced by small animals. The magnetocardiogram produced by a rate was measured and topographies of the P wave, QRS wave, and T wave were obtained. Auditory evoked magnetic fields were obtained and differences in the wave forms in both sides of the right ear were observed.

Magnetic force microscopy (MFM) is a technique used to study microscopic magnetic phenomena, and has wide use in the commercial hard disk industry. a form of MFM has been developed using a commercial piezoelectric quartz tuning fork (PQTF) to detect magnetic forces. The design is simple and inexpensive and its small size makes it suitable for studies undertaken in confined spaces.

A criterion for determining the maximum spacing between magnetometers for measuring the magnetic field is derived. A two-dimensional (2-D) filter model is employed to determine the maximum spatial frequency component present in the magnetic field that is above the spectral noise level. This maximum frequency component is then sampled at a rate greater than twice per period as indicated by the Nyquist criterion, yielding the required magnetometer spacing. It is shown that the rule-of-thumb employed in current clinical biomagnetic array systems, that the spacing between the coils should be approximately equal to the depth of the source, is adequate when the signal-to-noise power ratio is less than 28.4 (14.5 dB). The analysis also quantitatively demonstrates that reducing the separation between the measurement and source planes has a greater effect on the resolution than decreasing the noise level by the same factor. This result is important for employing high [T.sub.c] superconductor magnetometers that allow thinner thermal insulating layers at the cost of higher thermal noise.

The absolute measurement of magnetization in thin magnetic specimens at nanometer spatial resolution has been made possible by implementing two off-axis holography modes in a scanning transmission electron microscope (STEM). The absolute mode of STEM holography displays a linear change in phase difference for regions with constant magnetization and the slope determines the absolute value of magnetization in the specimen. The differential mode of STEM holography displays a constant value of phase difference for regions with constant magnetization, which simplifies the identification of magnetic structures in the specimen and the determination of domain wall profiles. Taking into account the high spatial resolution of a STEM instrument, STEM holography provides a valuable tool for quantitative investigations of magnetic structures at the nanometer level.

Vibrating sample magnetometer test of two magnetic samples confirm the efficacy of Preisach hysteresis model involved in superconductive hysteresis evaluation. Closed minor hysteresis loops in the magnetic field cycle confirm the wiping out function of the superconductive hysteresis and the magnetic field extrema in the two tested samples.

Mossbauer spectroscopy, X-ray and vibrating sample magnetometer studies of Co-Sn substituted BaFe(12-2x)Co(x)Sn(x)O(19) barium ferrite particles, with x ranging from 0 to 1.4, reveal magnetoplumbite structure of the particles and the iron ion particle number as a function of x. Reduced anisotropy constants are evaluated from the site performance of Co2+, Sn2+ ions and the simple-ion model.

The voltage induced in pickup coils by in general non-uniformly magnetized samples of finite size, which vibrate with large amplitude in arbitrary direction, is calculated. A system for the measurement of the dipole vector is proposed. Its minimum full scale range is [10.sup.-7][Am.sup.2] for the z-component and it is optimized in order to suppress octupole contributions. The errors of sample displacement and of misaligned vibration axis are well below 1%.

In this study we report on our continued investigation of particulate dispersion characterisation using magnetic measurement techniques. A fully automated vibrating sample magnetometer (VSM) was used to measure the reverse demagnetisation remanence curves of a 'wet' metal particle dispersion as a function of dispersion milling time. Theoretical interpretation of the data using a Brownian motion relaxation mechanism indicates that increases in milling time significantly reduce the mean size of the particle aggregates.

This paper introduces a useful application of magnetometer sensor to measuring movements of tongue points during speech. The magnetic sensing system developed here is design refinements with higher performances of an earlier prototype system. The system consists of magnetometer sensor units having amorphous wire cores and small permanent magnetic rods as pellets which are attached to the tongue points to be measured. Experiments were done on the two points of the tongue surface and characteristic patterns of articulatory gesture were observed on each point.

It is known that the torsion pendulum method provides a possibility to obtain the anisotropy field strength and the saturation magnetization of magnetically hard materials. Now this method is extended to obtain additionally the degree of texture. Theoretical calculations are compared with measurements performed on Nd-Fe-B sintered magnets at various temperatures. Error sources are discussed.

Ahigh resolution miniature flux-gate magnetometer was used to measure trapped flux distribution in a BiSrCaCuO high-Tc superconductor cooled to 77 K. The results showed that when the frequency of the ac magnetic field increased, there was a deterioration in the trapped flux amplitude. The amplitude was as small as 2 mG for a 50 Hz ac field and 43 mG for a 0.5 Hz ac field.

Surface oxidation of the CoFe and CoFeB bottom electrodes is detected by using magnetometry measurements of exchange bias (EB) characterizations that have included the EB field, training effect, uncompensated spin density and enhanced coercivity. The variations in the parameters are related to the surface oxidation of the bottom electrode and the annealed samples have shown evidence for an oxygen migration back to the MgO tunnel barrier by annealing.

A combination of a vibrating sample magnetometer and the scanning electron microscopy technique is employed to explain the preparation and the properties of the surface modified carbonyl iron particles. The magnetorheology and the sedimentation behavior exhibited by these particles are also analyzed.

We derive a relation between the magnetization obtained using a vibrating sample magnetometer (VSM) or a superconducting quantum interference device magnetometer (SQUID) and the magnetization obtained using a Faraday balance (FB). We show that, to a first approximation, the magnetization obtained using a FB should be very close to those obtained using VSM or SQUID especially for short samples and low fields. The variation of the magnetization with the sample length is presented at low and intermediate fields.

Several magnetometry studies are conducted to explain the synthesis of an antiferromagnet-ferromagnet-antiferromagnet trilayer. The application of a relatively small magnetic field is shown to lead to severe changes in the spin structure of the system.

A vectorial vibrating sample magnetometer is used for examining the angular dependence of asymmetric magnetization reversal in exchange biased NiO/Ni bilayers. The irreversible magnetization switches of a large amount of antiferromagnetic grains in thin NiO layers are responsible for rotatable anisotropy, which has also affected the shape of the hysteresis loops and the range of angles with symmetric magnetization reversal.

Magnetic ordering of [Cd.sub.1-x][Fe.sub.x][Cr.sub.2][S.sub.4] with Cd replaced by Fe on tetrahedral (A) site is analyzed by using Mossbauer spectroscopy and vibrating sample magnetometer as a function of temperature and external magnetic field. The Mossbauer spectrum is explained by ferrous ion of Jahn-Teller ion induced distortion and the contribution of angular moment of [Fe.sup.2+] has increased the asymmetric line of Mossbauer spectra at 4.2 K.

Metamagnetic transitions in single crystal Tb[Ni.sub.2][B.sub.2]C are studied at 1.9 K with a Quantum Design torque magnetometer. Torque magnetometry has not only shown a different sequence of metamagnetic phases for fields near the easy axis from those near the hard axis, but also the different natures of a principal metamagnetic phase near the hard axis.

Magnetometry, x-ray, and neutron scattering are used for studying the structural and magnetic properties of a TbMn[O.sub.3] thin film grown on a [001] SrTi[O.sub.3] substrate by pulsed laser deposition. The results have shown that the ferromagnetism is an intrinsic property of the TbMn[O.sub.3] film.

Iron oxide nanoparticles are prepared via reverse micelle methods and the initial iron concentration is varied in order to examine the effect of the iron concentration on the resultant iron oxide nanoparticle size. Magnetic characterization by vibrating sample magnetometry and powder x-ray diffraction is performed to verify proper phase and material and insights are obtained for the reverse micelle method along with the ability to tune the nanoparticle size.

Fe-Ni based amorphous thin films are prepared by thermal evaporation and glancing angle x-ray diffraction studies have showed that the irradiated films retain their amorphous nature. Magnetic measurements using a vibrating sample magnetometer has displayed that the coercivity of the films has increased with an increase in the ion fluence and the ability to modify the magnetic properties via swift heavy ion (SHI) irradiation is used for applications in thin film magnetism.

Alternating gradient magnetometry is used for studying the room temperature ferromagnetism (RT-FM) in ZnO/Si thin films on implantation of [Ni.sup.2+] ions. Exchange interaction between the charge carriers generated because of thermal effects of ion implantation and the localized spins of Ni is shown to be the main factors behind RT-FM.

The effect on effective area and voltage modulation depth of a serial superconducting quantum interference device (SQUID) magnetometer is studied. The optimal performance and layout of the high-[T.sub.c] serial SQUID array are analyzed.

The magnetic properties of Co/MgO bilayers are studied as a function of several sputtering growth parameters by using a superconducting quantum interference device magnetometer. The studies have shown the high sensitivity of the magnetic properties of the oxidation of the Co layer and have identified the relevant parameters to optimize the MgO growth process.

The current status of high-[T.sub.c] superconducting quantum interference devices (SQUIDs) is discussed. High-[T.sub.c] SQUID magnetometers displaying magnetic field sensitivity of 3-50 fT/[Hz.sup.1/2] is shown by incorporating serial SQUID into the pickup loop of the magnetometers.

Byline: L. Mechin, Ch. Simon, R.A. Chakalov The surface magnetic domain patterns of a La2/3Sr1/3MnO3 film grown on a LSAT (001) substrate, where LSAT stands for (LaAlO3)0.3(Sr2AlTaO6)0.7, were observed by magnetic force microscopy (MFM) as a function of the temperature in the 300-360 K range at its remanent state. Magnetic stripe domains showing an up and down magnetic configuration were observed, thus indicating the existence of a small out-of-plane magnetisation component. The domain size was in the order of 300 nm and did not vary with temperature. However the magnetic contrast in the MFM phase images decreased as the temperature increased and vanished as it approached the Curie temperature of the film. MFM measurements were compared with magnetisation vs. temperature curves measured by superconducting quantum interference device magnetometer.

The calculations based on the fluctuation-dissipation theorem has allowed quantitative evaluation of magnetic field noise, either from current or magnetization fluctuations, inside enclosures made of high-permeability materials. The results are used for assessing noise from existing shields and for designing of new shields for precision measurements.

The stability of the magnetic state of individual elements within patterned nanoarrays has depended on the balance of interelement interactions and shape anisotropy. These effects are studied by ferromagnetic resonance and alternating gradient magnetometry to characterize large area hexagonal arrays of 20 nm thick 190 nm wide elliptical Permalloy elements.

The metamagnetic transitions in single-crystal Er[Ni.sub.2][B.sub.2]C are studied with Quantum Design torque magnetometer. The results have shown new metamagnetic states in Er[Ni.sub.2][B.sub.2]C.

Self-assembled arrays of nanospheres are used for patterning a Co/Pt multilayer into nanopillars. Soft x-ray magnetic scattering has helped in understanding the correlation between magnetic roughness and structural roughness and also in obtaining selective magnetometry of various magnetic elements.

The magnetorelaxometry (MRX) of various [Fe.sub.3][O.sub.4] nanoparticle suspensions is examined by using a differential fluxgate setup. The studies have shown that the model is suited for the estimation of the distribution of the hydrodynamic size of MNPs and clusters.

The magnetic and electronic properties of [Bi.sub.0.75][Ca.sub.0.25]Mn[O.sub.3] are examined using magnetometry, diffraction and muon spin relaxation methods. The results have shown a ground state in [Bi.sub.0.75][Ca.sub.0.25]Mn[O.sub.3] distinct to [Bi.sub.0.75][Sr.sub.0.25]Mn[O.sub.3].

X-ray diffraction and magnetic force microscopy are used for characterizing texture and magnetic domain structure for a BaO[([Fe.sub.2][O.sub.3]).sub.6] film deposited on (0001) SiC with an MgO (111) template layer. The vector magnetization processes due to combination of domain wall motion and magnetization rotation are characterized by two dimensional vector coil vibrating sample magnetometry (VVSM).

The charge ordering effect in Lu[Fe.sub.2][O.sub.4] powder is examined with the vibrating sample magnetometer and Mossbauer spectroscopy. The Mossbauer spectra have shown that the asymmetry below 370 K is because of the charge ordering effect between [Fe.sup.2+] and [Fe.sup.3+].

The changes in saturation moment and crystal structure of elongated Cr[O.sub.2] nanoparticles upon galvanostatic electrochemical Li insertion are examined by using vibrating sample magnetometry. The studies have shown that the rutile structure is preserved on Li insertion, although the peaks have become broader and shoulder has appeared at high Li contents.

The development and performance analysis of an all-optical magnetometric technique based on nonlinear magneto-optical rotation with amplitude-modulated light is reported. The method allows to measure sensitive magnetic field in a broad dynamic range.

A SQUID (superconducting quantum interference device) magnetometry was used perform synthesis and characterization of different types of high-spin nitroxide radicals. The result provides insight into the impact of electron-electron spin-spin interactions on electron spin relaxation rates for nitroxide radicals.