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Kreines, N. M.

Publications and source records attributed to Kreines, N. M..

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Effect of Cr Spacer on Structural and Magnetic Properties of Fe/Gd Multilayers

Here, we analyze the role of a thin Cr spacer between Fe and Gd layers on the structure and magnetic properties of a [Fe(35 Å)/Cr(t Cr )/Gd(50 Å)/Cr(t Cr )] 12 superlattice. Samples without the Cr spacer (t Cr = 0) and with a thin spacer (t Cr = 4 Å) are investigated using X-ray diffraction, polarized neutron and resonance X-ray magnetic reflectometry, static magnetometry, magneto-optical Kerr effect, and ferromagnetic resonance techniques. Magnetic properties are studied experimentally in a wide temperature range 4–300 K and analyzed theoretically using numerical simulation on the basis of the mean-field model. We show that a reasonable agreement with the experimental data can be obtained considering temperature dependence of the effective field parameter in gadolinium layers. In conclusion, the analysis of the experimental data shows that besides a strong reduction of the antiferromagnetic coupling between Fe and Gd, the introduction of Cr spacers into Fe/Gd superlattice leads to modification of both structural and magnetic characteristics of the ferromagnetic layers.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Laser Fluence on Magnetic Properties of Thin Mn{sub x}Si{sub 1 –} {sub x} (x ≈ 0.5) Films Prepared by Pulsed Laser Deposition

Abstract—The effect of laser pulse energy E on the possibility of forming of a homogeneous “high-temperature” ferromagnetic phase in Mn{sub x}Si{sub 1 –} {sub x} (x ≈ 0.5) alloy films grown by pulsed laser deposition onto an Al{sub 2}O{sub 3} (0001) substrate has been studied. The high-temperature phase with manganese concentration x ≈ 0.53 and the Curie temperature T{sub C} ~ 200–300 K is shown to form near the substrate at the initial stage of the film growth. In this case, high values E ≥ 6.8 J/cm{sup 2} favor the stabilization of this phase over all film thickness, while low values E = 2.6–5.7 J/cm{sup 2} lead to a decrease in the manganese concentration in the upper film layer and the formation of additional “low–temperature” phase with T{sub C} ≈ 30–50 K provided by silicides MnSi and Mn{sub 4}Si{sub 7} crystallites.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Interlayer coupling in Fe/Cr/Gd multilayer structures

The effect of the chromium layer thickness on the magnetic state of an [Fe/Cr/Gd/Cr]{sub n} multilayer structure is studied. A series of Fe/Cr/Gd structures with Cr spacer thicknesses of 4–30 Å is studied by SQUID magnetometry and ferromagnetic resonance in the temperature range 4.2–300 K. The obtained experimental results are described in terms of an effective field model, which takes into account a biquadratic contribution to the interlayer coupling energy and a nonuniform magnetization distribution inside the gadolinium layer (which was detected earlier). Depending on the magnetic field and temperature, the following types of magnetic ordering are identified at various chromium layer thicknesses: ferromagnetic, antiferromagnetic, and canted ordering. A comparison of the experimental and calculated curves allowed us to determine the dependence of the bilinear (J{sub 1}) and biquadratic (J{sub 2}) exchange constants on chromium layer thickness t{sub Cr}. Weak oscillations at a period of about 18 Å are detected in the J{sub 1}(t{sub Cr}) dependence in the range 8–30 Å. The interlayer coupling oscillations in the system under study are assumed to be related to the RKKY exchange interaction mechanism via the conduction electrons of Cr.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗