摘要:

Resistance noise has been measured in thin films of La0.6Y0.07Ca0.33MnO3at the ferromagnetic metal to paramagnetic‐insulator transition where a large magnetoresistance is observed. Fluctuations in resistance were found to have a 1/fpower law form throughout the transition wherefis frequency. This intrinsic 1/fnoise is much larger than what is typical for metallic films and is consistent with the fluctuation‐dissipation theorem and magnetization fluctuations in the ferromagnetic phase. The implications of this large low frequency noise for practical magnetoresistive devices will be addressed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115757

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Positivegiant magnetoresistance (GMR), &Dgr;&rgr;/&rgr;, is reported here in polycrystalline antiferromagnetic materials RE2Ni3Si5(RE=Tb, Sm, Nd); &Dgr;&rgr;/&rgr;, at 4.4 K and in a field of 45 kOe, is 85%, 75%, and 58%, respectively. Positive GMR of such large magnitude has not been reported earlier in magnetically orderedpolycrystallinecompounds. The observed GMR is not correlated to the RE‐moments. It is, however, associated with the magnetic ordering of the lattice as its magnitude is significantly reduced in the paramagnetic state. Surprisingly, MR in Y2Ni3Si5, a non‐magnetic rare earth analogue, is also relatively large (16% at 4.4 K; 45 kOe) and is even slightly higher than that of antiferromagnetically ordered Gd2Ni3Si5(12% at 4.4 K; 45 kOe). The layered structure of the materials is suggested to be responsible for the observed GMR. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115758

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Operation is demonstrated of a field‐effect transistor made of transparant oxidic thin films, showing an intrinsic memory function due to the usage of a ferroelectric insulator. The device consists of a high mobility Sb‐dopedn‐type SnO2semiconductor layer, PbZr0.2Ti0.8O3as a ferroelectric insulator, and SrRuO3as a gate electrode, each layer prepared by pulsed laser deposition. The hysteresis behavior of the channel conductance is studied. Using gate voltage pulses of 100 &mgr;s duration and a pulse height of ±3 V, a change of a factor of two in the remnant conductance is achieved. The dependence of the conductance on the polarity of the gate pulse proves that the memory effect is driven by the ferroelectric polarization. The influence of charge trapping is also observed and discussed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115759

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Three‐dimensional electron optical simulations were used to model scanning tunneling microscope (STM) lithography in resists under field emission conditions. This work focuses on the effect of resists, as dielectric layers, between the tip and conducting substrate on the operation of the STM. Simulations were performed for resist thicknesses of 1–50 nm and tip‐resist separations of 1–20 nm. For a fixed 10 nm tip‐resist separation, the axial electric field at the tip decreases by a factor of 2.3 over the resist thickness range. The results show that the tip‐resist separation must decrease with increasing resist thickness, to achieve the operating conditions and the energy of electrons entering the resist can be significantly less than the applied tip‐substrate bias. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115760

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Nitrogen doped fluorinated amorphous carbon thin films for low dielectric constant interlayer dielectrics have been investigated. The films were deposited with a parallel‐plate plasma enhanced chemical vapor deposition. Source gases were CH4, CF4, and N2. The thermal stability of the films can be improved by the addition of N2. X‐ray photoelectron spectroscopy (XPS) measurement revealed that the C‐N bonds were formed in the films with the addition of N2. The dielectric constant of the films was increased from 2.1 to 2.4 at the nitrogen concentration of 10%. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115761

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

An experimental investigation of the dipole interaction in a water‐free glass/oil electrorheological fluid under an alternating electric field is presented in this letter. The values of the dielectric constant &egr; and conductivity &sgr; of glass and oil with respect to the frequency of the external electric field are measured, respectively. Corresponding to the changes in &egr; and &sgr;, the square of the absolute dielectric mismatch parameter |&bgr;| {&bgr;=(&egr;˜p(&ohgr;)−&egr;˜f(&ohgr;)]/[&egr;˜p(&ohgr;)+2&egr;˜f(&ohgr;)], where &egr;˜=&egr;+&sgr;/i&egr;0&ohgr;, and subscriptspandfindicate the glass and oil} decreases as the frequency is increased. After comparing the variation tendency of the |&bgr;|2with the yield stress of the electrorheological (ER) fluid in a measured frequency range we found that they coincide very well. This result confirms that the polarization theory can explain the mechanism of the ER effect not only in a dc electric field but also in that with a wide frequency range. However, the interaction within the multipoles should be considered in an exact calculation. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115762

出版商:AIP    

年代:1996

数据来源: AIP