Some reasonable conjectures are made concerning the Gnite-temperature pair correlations of spins ... more Some reasonable conjectures are made concerning the Gnite-temperature pair correlations of spins with anisotropic antiferromagnetic coupling. These conjectures provide a general description of the ordering. Using them together with the Gnite value of the zero-temperature susceptibility, one obtains Sg &S3 «.. . 0. .. «S4 &Sl, where S =1-(-1)"co"+2Z(og, co~is the zero-temperature pair correlation, and s&" is the infinite-/ limit of~a~i). Bonner and Fisher's finitechain extrapolations for &oi are in agreement with this result. Using their values of cut (f = 1&2P&4&~) and the inequality, bounds are computed for u5. The further conjecture that the rate of decrease in the absolute value of the correlation with distance is monotonic leads to a contradiction near the Heisenberg limit. The role of co" in the inequality and its derivation is particularly interesting since the limit l~~followed by T-+ 0 of the pair correlation of spins separated by t-1 spins is probably zero and not co. When the correlations approximate their zero-temperature value out to a distance g such that (cps) =id"and decrease slowly thereafter with increasing separation, then Tx is approximately zero.
The results of a model calculation of the orientation, magnetic Geld, and temperature dependence ... more The results of a model calculation of the orientation, magnetic Geld, and temperature dependence of the specinc heat C of CeCut; are found to be in good agreement with single-crystal data of Amato et u/. The model incorporates both Kondo and crystal-6eM eNects. It is suggested that the low-temperature Wilson's ratio C/TX, where X is the susceptibility, may not change in an applied Seld H and that both C/T and X at low temperatures as a function of H may be proportional to the many-body density of states at the energy pH. Heavy-fermion systems'2 have a very large term in their low-temperature speci6c heat which is linear in the temperature, i.e. , of the form yT. They were given this name since such a large linear term can be viewed as resulting from electronic excitations into a narrow, fiat band at the Fermi surface. Electrons in such a band would have a heavy mass. The considerable interest heavy fermions have received is in part due to their unusual superconducting properties. '
Abstract : The present invention is, in one aspect, a high anisotropy magnetic composite, having ... more Abstract : The present invention is, in one aspect, a high anisotropy magnetic composite, having a plurality of ferromagnetic particles, where these ferromagnetic particles are disposed within an antiferromagnetic material, which may either be a coating for the particles, or a matrix in which the particles are disposed; and a matrix material (antiferromagnetic or otherwise). Typically, this material will be disposed on a substrate. In another aspect, the invention is a method for magnetically recording data, comprising the step of exposing a magnetic recording medium according to the invention to a writing magnetic field. In another aspect, the invention is a method for reading magnetically recorded data, comprising the steps of positioning a read head in proximity to a magnetic recording medium according to the invention, where the read head can read the magnetization of a region on the magnetic recording medium, and translating the read head relative to the magnetic recording medium, where the read head is thus sequentially brought into proximity to a plurality of separately written regions on the magnetic recording medium.
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any fo... more All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 66.249.72.134-23/04/12,18:21:51) ... 136 Metastable, Mechanically Alloyed and ...
Oxidation resistant particles composed of copper and at least one metal having a valence of +2 or... more Oxidation resistant particles composed of copper and at least one metal having a valence of +2 or +3 and having an intermediate lattice energy for the metal in its hydroxide form are presented. The metal is selected from nickel, cobalt, iron, manganese, cadmium, zinc, tin, magnesium, calcium and chromium. In one embodiment, the phases of copper and at least one
present a new approach for storing information based on bits with different values for their magn... more present a new approach for storing information based on bits with different values for their magnetic permeability. Unlike present magnetic recording, information stored in this way should be ideal for archiving since it is unaffected by exposure to a magnetic field or moderate changes of temperature. Using heating with laser pulses as short as 100 µ sec, we have decreased the permeability of micron sized bits of an amorphous ferromagnet, Metglas, by crystallizing them. The permeability of micron sized bits of Cu/permalloy bilayers was decreased by using ohmic heating to cause the Cu to diffuse into the permalloy (80% Ni 20% Fe). This occurs because Ni is no longer ferromagnetic if the Ni atoms have too many Cu neighbors. The changes in the permeability are read by using either a magnetic tunnel junction or a spin transfer oscillator to measure whether the flux lines of a probe field are affected by the bits. The permeability of Cu/permalloy bilayers is not affected by 10 mega rads of gamma radiation from Co 60. Using heat assisted recording (HAMR) will permit writing permeability bits on a nm scale.
ABSTRACT The sensor element of magnetoelectric (ME) sensors generate an output with requiring an ... more ABSTRACT The sensor element of magnetoelectric (ME) sensors generate an output with requiring an input energy. In addition they are relatively sensitive, but in common with most other magnetic sensors, their performance deteriorates at low frequency. We have found that, by applying an additional higher frequency, magnetic modulation field to ME sensors, we can increase the sensitivity by a factor of 10 at l Hz. When a modulation field is applied, the signal appears as sidebands around the modulation frequency. A further improvement can be achieved if one adjusts the modulation frequency so that the sideband occurs at the mechanical resonant frequency of the sensor. Using this modulation, ME sensors can detect 4 pT/√Hz at 1 Hz in an unshielded room. We have found that we can increase the resonant frequency of asymmetric ME sensors by using a weight to apply a restoring torque. These sensors can also detect acoustic disturbances. By sweeping a magnetic field at the same time one is applying either a magnetic or acoustic field, one can distinguish between acoustic and magnetic sources.
Abstract Specific heat measurements on Kondo alloys Ce x La 1− x in the superconducting state sho... more Abstract Specific heat measurements on Kondo alloys Ce x La 1− x in the superconducting state show the existence of a γ T term which is linear in Ce concentration for 0.0075⩾ x ⩾0.002. The magnitude of γ is in agreement with the prediction based on previous electron tunneling measurements. There is a critical concentration ( x ≈ 0.001) below which there is an energy gap; i.e., γ = 0. This implies that a single impurity cannot locally destroy the energy gap.
This work provides an overview of strongly correlated electron systems. Taking a historical point... more This work provides an overview of strongly correlated electron systems. Taking a historical point of view, this work emphasizes early papers and general concepts that have remained relevant over the 50-year development of the field. Selected experimental results are given that illustrate different phenomena. The subjects discussed include concentrated Kondo systems, anomalous gapless superconductivity, non-Fermi liquid behavior, and quantum phase transitions.
Abstract : Finding human infrastructure elements such as machinery, chemicals, radiofrequency emi... more Abstract : Finding human infrastructure elements such as machinery, chemicals, radiofrequency emissions, electrical currents, or other evidence of human activity in confined enclosed spaces is a deficiency in current intelligence, surveillance, and reconnaissance (ISR) systems. In addition, operations in these places present a threat to Soldiers and detection of these manmade infrastructure elements is a needed capability. In this effort, the authors investigate and demonstrate multimodal, low-cost sensing on a mobile platform for detecting the presence of manmade "infrastructure" (i.e., machinery, electric currents, chemicals, hazardous materials, computers, and humans themselves) in hidden and confined spaces such as tunnels, sewers, caves, bunkers, and buildings, and in urban environments. The Human Infrastructure Detection and Exploitation (HIDE) Army Technology Objective (ATO) will use a variety of low-cost sensors, including acoustic, seismic, magnetic, electrostatic (E-field), passive infrared (PIR), chemical, radiofrequency, and optical. The HIDE ATO will develop the algorithms and sensor fusion capabilities, but will not develop the sensors themselves. The algorithms will be structured to be adaptable to varying combinations of sensor modalities, environmental conditions, and varying missions. The algorithms and sensors will be integrated on a small mobile unmanned ground vehicle (UGV). The ATO will not develop the platform or robotic controls, but it will leverage the ongoing Command & Control for Complex & Urban Terrain (C2CUT) ATO and other UGV efforts, and will integrate sensors onto an existing system. The ability to use many sensors and process the data at the sensor node will provide new ISR and Force Protection capabilities for the U.S. Army.
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188),
Some reasonable conjectures are made concerning the Gnite-temperature pair correlations of spins ... more Some reasonable conjectures are made concerning the Gnite-temperature pair correlations of spins with anisotropic antiferromagnetic coupling. These conjectures provide a general description of the ordering. Using them together with the Gnite value of the zero-temperature susceptibility, one obtains Sg &S3 «.. . 0. .. «S4 &Sl, where S =1-(-1)"co"+2Z(og, co~is the zero-temperature pair correlation, and s&" is the infinite-/ limit of~a~i). Bonner and Fisher's finitechain extrapolations for &oi are in agreement with this result. Using their values of cut (f = 1&2P&4&~) and the inequality, bounds are computed for u5. The further conjecture that the rate of decrease in the absolute value of the correlation with distance is monotonic leads to a contradiction near the Heisenberg limit. The role of co" in the inequality and its derivation is particularly interesting since the limit l~~followed by T-+ 0 of the pair correlation of spins separated by t-1 spins is probably zero and not co. When the correlations approximate their zero-temperature value out to a distance g such that (cps) =id"and decrease slowly thereafter with increasing separation, then Tx is approximately zero.
The results of a model calculation of the orientation, magnetic Geld, and temperature dependence ... more The results of a model calculation of the orientation, magnetic Geld, and temperature dependence of the specinc heat C of CeCut; are found to be in good agreement with single-crystal data of Amato et u/. The model incorporates both Kondo and crystal-6eM eNects. It is suggested that the low-temperature Wilson's ratio C/TX, where X is the susceptibility, may not change in an applied Seld H and that both C/T and X at low temperatures as a function of H may be proportional to the many-body density of states at the energy pH. Heavy-fermion systems'2 have a very large term in their low-temperature speci6c heat which is linear in the temperature, i.e. , of the form yT. They were given this name since such a large linear term can be viewed as resulting from electronic excitations into a narrow, fiat band at the Fermi surface. Electrons in such a band would have a heavy mass. The considerable interest heavy fermions have received is in part due to their unusual superconducting properties. '
Abstract : The present invention is, in one aspect, a high anisotropy magnetic composite, having ... more Abstract : The present invention is, in one aspect, a high anisotropy magnetic composite, having a plurality of ferromagnetic particles, where these ferromagnetic particles are disposed within an antiferromagnetic material, which may either be a coating for the particles, or a matrix in which the particles are disposed; and a matrix material (antiferromagnetic or otherwise). Typically, this material will be disposed on a substrate. In another aspect, the invention is a method for magnetically recording data, comprising the step of exposing a magnetic recording medium according to the invention to a writing magnetic field. In another aspect, the invention is a method for reading magnetically recorded data, comprising the steps of positioning a read head in proximity to a magnetic recording medium according to the invention, where the read head can read the magnetization of a region on the magnetic recording medium, and translating the read head relative to the magnetic recording medium, where the read head is thus sequentially brought into proximity to a plurality of separately written regions on the magnetic recording medium.
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any fo... more All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 66.249.72.134-23/04/12,18:21:51) ... 136 Metastable, Mechanically Alloyed and ...
Oxidation resistant particles composed of copper and at least one metal having a valence of +2 or... more Oxidation resistant particles composed of copper and at least one metal having a valence of +2 or +3 and having an intermediate lattice energy for the metal in its hydroxide form are presented. The metal is selected from nickel, cobalt, iron, manganese, cadmium, zinc, tin, magnesium, calcium and chromium. In one embodiment, the phases of copper and at least one
present a new approach for storing information based on bits with different values for their magn... more present a new approach for storing information based on bits with different values for their magnetic permeability. Unlike present magnetic recording, information stored in this way should be ideal for archiving since it is unaffected by exposure to a magnetic field or moderate changes of temperature. Using heating with laser pulses as short as 100 µ sec, we have decreased the permeability of micron sized bits of an amorphous ferromagnet, Metglas, by crystallizing them. The permeability of micron sized bits of Cu/permalloy bilayers was decreased by using ohmic heating to cause the Cu to diffuse into the permalloy (80% Ni 20% Fe). This occurs because Ni is no longer ferromagnetic if the Ni atoms have too many Cu neighbors. The changes in the permeability are read by using either a magnetic tunnel junction or a spin transfer oscillator to measure whether the flux lines of a probe field are affected by the bits. The permeability of Cu/permalloy bilayers is not affected by 10 mega rads of gamma radiation from Co 60. Using heat assisted recording (HAMR) will permit writing permeability bits on a nm scale.
ABSTRACT The sensor element of magnetoelectric (ME) sensors generate an output with requiring an ... more ABSTRACT The sensor element of magnetoelectric (ME) sensors generate an output with requiring an input energy. In addition they are relatively sensitive, but in common with most other magnetic sensors, their performance deteriorates at low frequency. We have found that, by applying an additional higher frequency, magnetic modulation field to ME sensors, we can increase the sensitivity by a factor of 10 at l Hz. When a modulation field is applied, the signal appears as sidebands around the modulation frequency. A further improvement can be achieved if one adjusts the modulation frequency so that the sideband occurs at the mechanical resonant frequency of the sensor. Using this modulation, ME sensors can detect 4 pT/√Hz at 1 Hz in an unshielded room. We have found that we can increase the resonant frequency of asymmetric ME sensors by using a weight to apply a restoring torque. These sensors can also detect acoustic disturbances. By sweeping a magnetic field at the same time one is applying either a magnetic or acoustic field, one can distinguish between acoustic and magnetic sources.
Abstract Specific heat measurements on Kondo alloys Ce x La 1− x in the superconducting state sho... more Abstract Specific heat measurements on Kondo alloys Ce x La 1− x in the superconducting state show the existence of a γ T term which is linear in Ce concentration for 0.0075⩾ x ⩾0.002. The magnitude of γ is in agreement with the prediction based on previous electron tunneling measurements. There is a critical concentration ( x ≈ 0.001) below which there is an energy gap; i.e., γ = 0. This implies that a single impurity cannot locally destroy the energy gap.
This work provides an overview of strongly correlated electron systems. Taking a historical point... more This work provides an overview of strongly correlated electron systems. Taking a historical point of view, this work emphasizes early papers and general concepts that have remained relevant over the 50-year development of the field. Selected experimental results are given that illustrate different phenomena. The subjects discussed include concentrated Kondo systems, anomalous gapless superconductivity, non-Fermi liquid behavior, and quantum phase transitions.
Abstract : Finding human infrastructure elements such as machinery, chemicals, radiofrequency emi... more Abstract : Finding human infrastructure elements such as machinery, chemicals, radiofrequency emissions, electrical currents, or other evidence of human activity in confined enclosed spaces is a deficiency in current intelligence, surveillance, and reconnaissance (ISR) systems. In addition, operations in these places present a threat to Soldiers and detection of these manmade infrastructure elements is a needed capability. In this effort, the authors investigate and demonstrate multimodal, low-cost sensing on a mobile platform for detecting the presence of manmade "infrastructure" (i.e., machinery, electric currents, chemicals, hazardous materials, computers, and humans themselves) in hidden and confined spaces such as tunnels, sewers, caves, bunkers, and buildings, and in urban environments. The Human Infrastructure Detection and Exploitation (HIDE) Army Technology Objective (ATO) will use a variety of low-cost sensors, including acoustic, seismic, magnetic, electrostatic (E-field), passive infrared (PIR), chemical, radiofrequency, and optical. The HIDE ATO will develop the algorithms and sensor fusion capabilities, but will not develop the sensors themselves. The algorithms will be structured to be adaptable to varying combinations of sensor modalities, environmental conditions, and varying missions. The algorithms and sensors will be integrated on a small mobile unmanned ground vehicle (UGV). The ATO will not develop the platform or robotic controls, but it will leverage the ongoing Command & Control for Complex & Urban Terrain (C2CUT) ATO and other UGV efforts, and will integrate sensors onto an existing system. The ability to use many sensors and process the data at the sensor node will provide new ISR and Force Protection capabilities for the U.S. Army.
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188),
Uploads
Papers by Alan Edelstein