摘要:

Optically pumped InAs/InGaSb/InAs/AlSb type-II quantum well lasers emitting from 4.1 to 4.36 &mgr;m were operated up to 226 K with a characteristic temperatureT0of 30 K. The absorbed threshold pump intensity at 0.98 &mgr;m was0.12 kW/cm2at 100 K, and3.25 kW/cm2at 200 K with a pulse length of 5 &mgr;s and a repetition rate of 2 kHz. At 73 K, the peak output power was 250 mW per facet with a pulse length of 10 &mgr;s and a repetition rate of 10 kHz. A cw output power of 14.7 mW was observed at 74 K. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120313

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The persistent photoinduced changes in the critical temperatureTCand the normal state conductivity of(Y0.5Ca0.5)Ba2Cu3O&dgr;thin films are studied. Previously such effects have been observed only in underdopedYBa2Cu3O&dgr;orYSrxBa2−xCu3O&dgr;,which always lead to the enhancement of bothTCand conductivity. The current system can be doped from the underdoped regime to the overdoped regime by increasing its oxygen content. The photoinducedTCreduction in the overdoped films is observed. The simultaneous enhancement of conductivity is consistent with the interpretation that photoillumination always increases hole concentration in the “123” systems. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120323

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The magnetic field dependence of the critical currentIC(B)and the remanent magnetization of several multifilamentary(BiPb)2Sr2Ca2Cu3Oxtapes were measured. The low field behavior ofIC(B)is interpreted by the self-field effect, whereas at higher fields, the field dependence for all tapes was found to be identical except for a constant factor. Although self-field transport critical current densitiesjC0differed widely for the tapes, the intergranular critical current densities determined from remanent magnetization were found to be equal. The results indicate that the reduction ofjC0by macroscopic defects is an important factor, whereas locally the filaments are of high quality. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120314

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We succeed in preparing anisotropic magnetic powders with high performance based on theNdFe10.5Mo1.5Nxnitrides. The properties of these materials are favorable for permanent magnet application. The domain structures of theNdFe10.5Mo1.5andNdFe10.5Mo1.5Nxwere studied by using magnetic force microscopy. Upon nitrogenation, a domain structure transition from complex maze to simple stripe was found. This transition is due to the strongly uniaxial magnetocrystalline anisotropy induced by interstitial nitrogen atoms. Together with magnetic measurements, we have calculated the domain wall energy &ggr;, exchange constantA, domain wall thickness &dgr;, and critical single-domain particle sizeDcofNdFe10.5Mo1.5andNdFe10.5Mo1.5Nx.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120315

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Electron beam deposited spikes for use in magnetic force microscopy have been grown onto atomic force microscope tips and coated with magnetic thin films using thermal evaporation. The resulting magnetically active regions are a close approximation to monopoles or dipoles located on the very end of the spikes. We show that these tips image with increased spatial resolution and less sample perturbation than the standard, commercially available tips. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120316

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Al/Fe/Al2O3/CoFe/Aljunctions with dimensions of2×2–40×40 &mgr;m2were prepared on a 2 in. Si wafer using conventional photolithography and ion-beam etching. The junction trilayers were deposited sequentially without breaking vacuum and a tunnel barrier wasin situnaturally oxidized. The resultant junction resistance scaled linearly with the junction area over all dimensions used. Normalized resistance of less than1.5×10−5 &OHgr; cm2was obtained in maintaining a magnetoresistance (MR) ratio of about 5&percent;. The resistance values are much smaller than ever reported and close to those required for an MR head device. The MR ratio exhibited no significant change up to at least1×103 A/cm2with increasing junction current density. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120317

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Giant magnetoresistance (GMR) effects up to 10&percent; have been observed in Co/Cu/FeNi spin valve structures grown onto step bunched vicinal Si(111) substrates misoriented towards [11-2]. The step bunching is activated using a simple thermal treatment which leads to surfaces where terraces alternate with facets at the nanometer scale. GMR of the spin valve structures is investigated with the current applied parallel or perpendicular to the steps. An in-plane uniaxial magnetic anisotropy is induced in each magnetic layer with the easy axis parallel to the steps. This results in square GMR behavior when the field is applied along the easy axis. Specific features observed when the field is applied along the hard axis are also shown to be the consequence of this anisotropy. When the initial misorientation angle of the substrate becomes higher than 4°, we observe an enhancement of the room-temperature GMR when the current is applied perpendicular to the steps. The origin of this enhancement is discussed based on the temperature dependence of this effect. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120318

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A simple dynamical model for studying the charging of substrates irradiated by particle beams is developed. The charging potential for positive ion beams can be as large as the beam voltage. For negative ion beams, the charging potential is significantly lower and is governed by the secondary electrons. A closed form expression derived for the charging voltage in the case of negative ion beams agrees well with our numerical work. The results are consistent with observations on charging of isolated substrates during ion implantation with positive and negative ion beams. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120319

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The work functions of solid layers of various thicknesses of dithioketopyrrolopyrrole (DTPP), evaporated onSnO2:F,were measured by the Kelvin probe technique. Surface photovoltage (SPV) measurements confirm thep-conductivity type. By front and back side illumination of the thick DTPP layers, two space-charge layers are distinguished, allocated to the air/DTPP and DTPP/SnO2:Finterface, respectively. The SPV of thinner layers is a superposition of the front side signal and back side signal, modulated by a filter effect through the organic layer. This permitted the construction of the energy diagram of the DTPP/SnO2:Fjunction. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120322

出版商:AIP    

年代:1997

数据来源: AIP