摘要:

Wall displacements are induced by large current pulses crossing a wall, in Ni81Fe19films. In films of thicknessw<35 nm containing Ne´el walls, the sense of wall motion is found to be independent of the magnetization sense in the two domains adjacent to the wall, and is identical to the sense of motion of the electronlike charge carriers. This shows that the wall motion is not caused by stray magnetic fields, but rather bys‐dexchange forces generated by conduction electrons. The value &bartil;5×107A cm−2of the needed current density agrees with predictions of a theory based ons‐dexchange. In the case of cross‐tie walls in films with 35 nm <w<86 nm, the sense of wall motion does depend on the sense of the domain magnetizations. The force of the circumferential magnetic field of the current is probably important, here.

ISSN:0021-8979    

DOI:10.1063/1.340201

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We have measured the electrical‐transport and magnetic properties of several intermetallic compounds UTSn and UTSb, where T is a transition metal. The electrical resistivity is up to three orders of magnitude larger than usually found for U‐based compounds. This is ascribed to the occurrence of a spin polarized energy gap related to the MgAgAs‐type crystal structure. For UNiSn at least one spin band closes at low temperature, resulting in half‐metallic behavior. Interestingly, the magnetic properties exhibit Kondo‐lattice character and weak‐moment ordering.

ISSN:0021-8979    

DOI:10.1063/1.340202

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Measurements of the thickness dependence of the electrical resistance of two very thin Cr films deposited at substrate temperatures of 385 and 360 °C and pressures of 4×10−7and 10−6Torr are reported. Preliminary measurements of the thickness dependence of the Ne´el temperature (TN) of the film deposited at 360 °C at thicknesses ≥10 nm are also presented. In these two films the resistance in the thickness region 2≤d≤7.5 nm can be very well described byR∝[(d/dc)−1]−twithdcequal to 1.64±0.20 and 1.03±0.20 nm, respectively, andt=1.34±0.11. The Ne´el temperatures show a turning point around 14 nm in agreement with the known thickness dependence of the stress.dTN/dSthas been found to be ∼100 K/kbar whereStis the internal tensile stress in the film.

ISSN:0021-8979    

DOI:10.1063/1.340203

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We review recent theoretical and experimental work on the metal to insulator transition in doped semiconductors. The spin excitations on the insulating side of the transition can be described in terms of a spin‐ 1/2 Heisenberg antiferromagnet with the spins randomly located in space. Numerical analysis of this Hamiltonian has led to a fairly complete understanding of the static spin susceptibility and the electron spin resonance spectrum. The physics on the metallic side far from the transition is also fairly well understood in terms of a recently developed theory of the disordered Fermi liquid. The physics near the transition point is, however, still not clear. All the experimental evidence indicates the presence of local electronic moments on the metallic side of the transition. Recent theoretical work and open problems in the description of such a metallic phase are briefly discussed.

ISSN:0021-8979    

DOI:10.1063/1.340204

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We have determined the components of the magnetoresistance tensor through fifth order in the magnetic direction cosines for four epitaxially grown iron films with thicknesses between 200 and 60 A˚ at 300, 77, and 4.2 K. We have also determined their magnetic anisotropy parameters from ferromagnetic resonance at 300 K. These phenomenological parameters provide an excellent description of the magnetic field dependence of the planar magnetoresistivity for electric current directed along the [001], [11¯0], and [11¯(2)1/2] directions and the applied fields necessary to produce spin flops.

ISSN:0021-8979    

DOI:10.1063/1.340205

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The thermal conductivityKof rare‐earth intermetallic compounds with magnetic ordering temperaturesT0below 100 K is a key parameter affecting their use in magnetic refrigerators and regenerators. We have measured the thermal conductivity of ErAl2,T0=12 K, between 5 and 170 K in 0‐ and 7‐T applied magnetic fields. The zero‐field results show a strong, 20‐K‐wide minimum in the thermal conductivity near the ordering temperature. The results at 7 T indicate that the magnetic field eliminates the minimum and produces a monotonic temperature dependence. We attribute these effects to magnetic scattering of electrons.

ISSN:0021-8979    

DOI:10.1063/1.340206

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The electrical resistivity of a series of Co‐Cr multilayered thin films (MLS) of equal layer thickness of ∼30–30 A˚ made at various substate temperatures and deposition rates of 0.5 and 2 A˚/s was measured over the temperature range of 4.2–350 K. The most striking feature seen in several of these MLS was that the bump near the Ne´el temperatureTNof the spin‐density wave (SDW) of Cr was 2–4 times greater than that seen inCrCo alloys. The bump in the MLS is also much sharper than that of the alloys. The resistivity bump and an increase inTNin the alloys has been attributed to an enhancement of the SDW due to the exchange interaction between the Co moments and the SDW. It is proposed that the even larger enhancement of the SDW in the MLS is due to the superlattice structure of the MLS. This changes the Cr Fermi surface by introducing new Brillouin zones and thus increases the nesting which gives rise to the SDW. The variation of theTNvalues of the MLS varies systematically with the substrate temperature. Other similarities and differences between the MLS and the alloys resistivity behavior are discussed.

ISSN:0021-8979    

DOI:10.1063/1.340207

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We report magnetoresistance (MR) measurements on Au/Co/Au sandwiches and Au/Co/Au multilayers, deposited on polished glass substrates in ultrahigh vacuum, with Co thickness ranging between 3 and 30 A˚. The experiments were performed at room temperature in the field range 0–0.8 T and at low temperature 1.3–4.2 K in the field range 0–5 T for different field orientations with respect to the film and to the current. For Co thickness below 11 A˚, the experimental data are consistent with an easy axis perpendicular to the film, in agreement with previous ferromagnetic resonance and magnetization measurements. From the hysteretic behavior of the MR, coercive fields of a few 102Oe at room temperature are observed. In Co bilayers, the MR is enhanced with respect to the MR of simple sandwiches and indicates a square hysteresis loop. The abnormally large MR of the ultrathin Co films is attributed to a Co/Au interface resistance related to walls between Co domains with alternating perpendicular magnetization.

ISSN:0021-8979    

DOI:10.1063/1.340208

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A series of amorphous Fe80−xMxB14Si6(M=Mn, V, Cr, andx=2, 4, 6, 8, 10, 12, and 14 at. %) alloys have been made by the spinning‐wheel method. We have measured the density &dgr;, saturation magnetizationMs, electrical resistivity &rgr;0, Hall resistivity &rgr;H, and magnetoresistance &Dgr;&rgr;/&rgr;0of each sample at room temperature. The anomalous Hall coefficientRsis determined from the relation &rgr;H=R0B+RsMs.Rsis found to vary asRs=A&rgr;1.70. The density, magnetization, and magnetoresistance are all decreasing functions ofx. The Curie temperatureTCis determined from the low‐field thermomagnetization data and the Arrott plot. The positive forced magnetoresistivities are discussed from the viewpoint of the current models.

ISSN:0021-8979    

DOI:10.1063/1.340209

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A new type of high‐resistivity soft magnetic amorphous alloy film with a very fine two‐phase heterostructure was found in cosputtered Fe‐B‐C films. These amorphous films are found to have a number of superior properties in the high‐frequency range (over∼10 MHz) over not only regular amorphous films, but also sendust film cores, which have already been applied to high‐density recording media having high coercivity. They were found to exhibit unique isotropic soft magneticB‐Hcurves with highBs(∼15 000 G), lowHc(∼0.3 Oe), and high &rgr; (∼400 &mgr;&OHgr; cm), and the reduced magnetization versus reduced temperature curve was almost the same as thej=∞ curve of the Brillouin function. A very high permeability with less core loss, especially in the high‐frequency range, was also experimentally observed in those amorphous films.

ISSN:0021-8979    

DOI:10.1063/1.340210

出版商:AIP    

年代:1988

数据来源: AIP