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1
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Giant Magnetoresistance in Permalloy/Copper Multilayers

100%
Luciński T., Stobiecki F.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
273-275
EN
The oscillatory behaviour of the giant magnetoresistivity versus Cu sublayer thickness was observed in Ni_{83}Fe_{17}/Cu multilayers with an oscillation period of 1 nm independently of buffer layer and substrates used in the experiment. The giant magnetoresistance field sensitivity equal to 0.02%/Oe and 0.15%/Oe for the first and the second maximum respectively, were found. It was shown that the giant magnetoresistance effect in our multilayers is not only due to the antiferromagnetic coupling between adjacent permalloy layers but also due to the superparamagnetic-like behaviour related to the existence of the intermixed interfacial areas.
2
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Content available

Multilayer Structures with Giant Magnetoresistance

100%
Stobiecki F., Stobiecki T.
Acta Physica Polonica A
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2002
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vol. 102
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issue 1
95-108
EN
The phenomenological description of the giant magnetoresistance effect as well as the discussion of the requirements which must be fulfilled in giant magnetoresistance thin film structures are given in the first part of our review. In the second part the magnetization reversal and giant magnetoresistance effect of antiferromagnetically coupled multilayers, spin valve and pseudo-spin valve thin film structures are explained. For these structures we also discuss the influence of the structure defects such as surface roughness and pinholes on the giant magnetoresistance effect.
3
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Magnetic Properties and GMR of Sputtered Permalloy/Au Multilayers

100%
Szymański B., Stobiecki F.
Acta Physica Polonica A
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2000
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vol. 97
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issue 3
535-538
EN
We report on structural, magnetic, and GMR properties of permalloy/Au multilayers where permalloy = Ni_{83}Fe_{17}, deposited by face-to-face sputtering onto Si(111) substrate. X-ray diffraction studies confirmed a good structural quality of our multilayers. The samples were characterised with vibrating sample magnetometer, longitudinal magnetooptical Kerr effect and giant magnetoresistance measurements. It was determined that our multilayers are magnetically very soft with H_{c} ≈ 1 Oe and show uniaxial anisotropy with H_{K} ≈ 5 Oe. For gold sublayer thickness d_{Au} close to 1.1 nm the antiferromagnetic coupling is present in very narrow Au thickness range (≈ 0.2 nm). Despite a good structural quality of samples relatively small giant magnetoresistance value (1.2% at room temperature) was found. It is due to non-perfect aniferromagnetic coupling caused by pinholes.
4
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Structure and Magnetic Propertics of Fe/Zr Multilayers

100%
Szymański B., Stobiecki F.
Acta Physica Polonica A
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1994
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vol. 85
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issue 2
455-459
EN
In this paper we report results of investigation into structure and magnetic properties of as-deposited Fe/Zr multilayers with different wavelength of modulation, λ, and thicknesses ratio of sublayers r = d_{Fe}/d_{Zr}. Three series of samples with r equal to 0.5, 1, 2 and λ from 12 nm to 1.2 nm were prepared by sputtering technique. The samples were studied by X-ray diffraction and torque curve measurements. It is shown that during deposition amorphization process takes place at interfaces. For nominal Fe sublayer thickness d_{Fe} smaller than 2 nm the multilayers are found to be completely amorphous independently of r, and consist of alternating Fe-rich and Fe-poor amorphous sublayers.
5
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Resistivity and Temperature Coefficient of Resistivity of the Fe/Zr Multilayer Films

100%
Luciński T., Stobiecki F.
Acta Physica Polonica A
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1994
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vol. 85
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issue 2
443-447
EN
The resistivity (ρ) and temperature coefficient of resistivity (TCR) dependencies on modulation wavelength (λ) were examined in Fe/Zr multi-layer thin films. It was shown that the ρ(λ) and TCR(λ) behaviours can be explained on the basis of the assumption that the amorphous phase can be spontaneously formed during the deposition process. We found that the effective thickness of the amorphous phase was ≈2 nm per single interface.
6
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Ferromagnetic Resonance in Fe/Zr Multilayers

100%
Dubowik J., Stobiecki F.
Acta Physica Polonica A
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1994
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vol. 85
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issue 2
449-453
EN
We report our ferromagnetic resonance measurements for three series of Fe/Zr multilayers with thickness ratio of Fe to Zr sublayers equal to 2:1, 1:1, and 1:2, respectively. These measurements may serve as an example of employing ferromagnetic resonance technique as a sensitive probe for monitoring the magnetic phases formed at interfaces in the earliest stages of the interdiffusion reaction in multilayer Fe/Zr films for which the onset of the amorphization takes place during deposition due to thermodynamics of the system. The resulting structure may be regarded as strongly inhomogeneous one that includes distinct ferromagnetic phases related to the Fe atoms in various surroundings.
7
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Superparamagnetic Grains as Source of Giant Magnetoresistance Effect in Discontinuous Co/Ag Multilayers

81%
Luciński T., Stobiecki F., Dubowik J., Czajka R.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
269-272
EN
The as-deposited and annealed Co/Ag discontinuous multilayer-like structures were examined. Discontinuous Co sublayers are thought to consist of fine superparamagnetic and ferromagnetic grains. Using the bimodal superparamagnetic grain sizes distribution the GMR(H) dependencies were successfully modelled with the use of two Langevin functions simulating the magnetization of the superparamagnetic grains.
8
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Exchange Coupled Double Layers for Magneto-Optical Applications

81%
Becker S., Rohrmann H., Roell K., Stobiecki F.
Acta Physica Polonica A
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1997
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vol. 91
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issue 1
55-65
EN
Optical data storage is a rapidly developing technique, which emerges in many varieties. Magneto-optical recording, in particular, applies amorphous rare earth/transition metal films, where a binary coded information is written thermomagnetically and is read by the magneto-optical Kerr or Faraday effect. To increase the writing speed and the recording density, techniques for direct overwrite and magnetically induced superresolution were proposed, which involve these of exchange coupled double layer systems as a storage media. In this paper, the principles and the properties of exchange coupled double layers are discussed with respect to the direct overwrite and the magnetically induced superresolution processes. A formalism based on a switching field diagram is developed yielding all information necessary to achieve reliable and practical writing procedures. As an example, the direct overwrite capability is demonstrated experimentally in antiparallel coupled layer systems.
9
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Giant Magnetoresistance of [Ni_{80}Fe_{20}/Au/Co/Au]_{N} Multilayers Deposited on Flexible Substrates

81%
Gospodarczyk W., Urbaniak M., Stobiecki F., Szymański B.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1234-1236
EN
Magnetic hysteresis and magnetoresistance of [Ni_{80}Fe_{20}/Au/Co/Au]_{10} multilayers displaying giant magnetoresistance and sputtered on a flexible polypropylene substrates (an adhesive tape) is investigated. The magnetoresistive properties are very similar to those found in films prepared under the same conditions on Si(100) substrates. It is demonstrated, too, that a bendability of the substrates can be utilized to form cylindrically shaped magnetoresistive sensors with reduced anisotropy of the effect.
10
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Magnetic Anisotropy and Magnetostriction Oscillations in Magnetic Multilayers

81%
Szymczak H., Żuberek R., Stobiecki F.
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vol. 96
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issue 3-4
495-499
EN
Interlayer pseudodipolar coupling between two ferromagnets separated by nonmagnetic spacer is analyzed. It was shown that this type of interaction should induce magnetic anisotropy and magnetostriction oscillations. It was also predicted that both magnetic anisotropy and magnetostriction decrease with an increase in the spacer thickness. This effect was observed in [permalloy/Cu]_{100} multilayers.
11
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Structure and Magnetic Properties of Ni/Ti Multilayers

81%
Szymański B., Stobiecki F., Otto T., Röll K.
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EN
We report a study of structure and magnetic properties of Ni/Ti multilayers with different modulation wavelength, 10 nm ≤ λ ≤ 40 nm, and constant sublayers thickness ratio d_{Ni}/d_{Ti}=1. Specimens were characterized with X-ray diffraction, vibrating sample magnetometer and torque meter in as-deposited state and in successive stages of isothermal annealing at 423 K. Hysteresis curves of as-deposited samples revealed the typical feature of ferromagnetic films with predominant shape anisotropy. During annealing very pronounced changes in the hysteresis loops were observed. An analysis of the loops indicates the occurrence of distinct changes in magnetic anisotropy of Ni sublayers: their effective shape anisotropy is drastically reduced due to a development of the perpendicular anisotropy and/or a modification of the microstructure. The effect can possibly be applied to achieve desirable variation of perpendicular anisotropy in multilayers which consist of Ni sublayers.
12
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Creation and Observation of Domain Structures with a Special Kerr Microscope

81%
Knappmann S., Röll K., Stobiecki F.
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EN
A Kerr microscope is presented, which on the one hand allows us to make, in a conventional manner, images of domains in thin films with perpendicular magnetic anisotropy. On the other hand, it is possible to heat the sample locally by a focussed laser beam and make images simultaneously. Therefore, it is possible to write domains thermomagnetically and further to observe temperature dependent magnetic reorientations. For demonstration domains have been created thermomagnetically in TbFe multilayers. Writing with low magnetic field leads to domains with a subdomain structure, as it has been found previously by Lorentz microscopy.
13
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Anisotropy Distribution in NiFe/Au/Co/Au Multilayers

71%
Dubowik J., Stobiecki F., Gościańska I., Kociemba M., Bednarski W.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
315-318
EN
We present results of FMR investigations of anisotropy distribution in uncoupled [NiFe/Au/Co/Au]_N structures with alternating in-plane (NiFe) and out-of-plane anisotropies (Co). It is concluded that for NiFe layers anisotropy distribution is negligible and can be increased by "dusting" of NiFe with ultrathin Co layers. The perpendicular anisotropy K_{U}^2 of Co layers depends on Co thickness in a standard way ∝ 1/d_{Co}, and is distributed in a range of ≈10-20% of K_{U}^2 (i.e., ≈ 1.5× 10^6 erg/cm^3).
14
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Selective Modification of Magnetic Properties of Co_1 /Au/Co_2/Au Multilayers by He Ion Bombardment

71%
Urbaniak M., Stobiecki F., Engel D., Szymański B., Ehresmann A.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
326-328
EN
We show that in a [Co_1/Au/Co_2/Au]_4 multilayer, where Co_{1(2)} denote Co layers of different thicknesses, a 10 keV He-ion bombardment with a 6×10^{14} ions cm^{-2} dose leads to changes of the easy direction from out-of-plane to in-plane in the thicker Co layers (t_{Co2} = 1 nm) while the perpendicular anisotropy of the thinner Co layers (t_{Co1} = 0.6 nm) is preserved. The investigated multilayers were obtained by sputtering and the thickness of the Au layers (t_{Au} = 4 nm) ensured that a direct coupling between the Co layers (through pinholes) and Ruderman-Kittel-Kasuya-Yosida-like interactions were negligible.
15
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Néel's Magnetostatic Coupling in Sputtered Cu/Py/V/Py/MnIr/Cu Multilayers

71%
Urbaniak M., Brückl H., Stobiecki F., Luciński T., Reiss G.
Acta Physica Polonica A
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2004
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vol. 105
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issue 3
307-313
EN
The correlation between magnetostatic or Néel's coupling and roughness of interfaces in sputtered Cu/Py/V/Py/MnIr/Cu multilayers was investigated with the help of atomic force microscopy and magnetometry. It is shown that the coupling strongly depends on the roughness of seed Cu layer which in turn depends on sputtering power. Roughness levels off after deposition of consecutive layers to about 0.2 nm rms.
16
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Changes of Structure and Magnetic Properties of (Ni_{80}Fe_{20}/Au/Co/Au)_N Multilayers as a Function of Repetition Number N

71%
Szymański B., Stobiecki F., Urbaniak M., Siffalovic P., Majkova E.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
205-208
EN
The influence of repetition number N on magnetoresistance, magnetic reversal and structure of sputtered (Ni_{80}Fe_{20}/Au/Co/Au)_N multilayers was investigated. The multilayers are characterized by in-plane (Ni_{80}Fe_{20}) and out-of-plane (Co) magnetic anisotropy of ferromagnetic layers and show considerable magnetoresistance effect (ΔR/R) of the giant magnetoresistance type. Increased N results in an enhancement of ΔR/R from about 0.5% for N=1 up to above 5% for N=15. This enhancement is caused by: diminishing the role of electron scattering at the surfaces, decreasing the effect of structural imperfection and the lack of the perpendicular anisotropy of Co layer in the first period. The interpretation is corroborated by low ΔR/R value observed for N=1 and an evolution of the ΔR(H)/R dependence with increasing N. The anisotropy field of Co layers also increases with N.
17
Content available remote

High-Quality Ni-Fe/Cu Multilayer Films with Antiferromagnetic Coupling

62%
Stobiecki F., Dubowik J., Luciński T., Szymański B., Rohrmann H., Röll K., Schmidt M.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
277-280
EN
We report structural and magnetic properties of Ni_{83}Fe_{17}/Cu multilayer films with various buffer layer and sublayer thicknesses of copper d_{Cu} and Permalloy d_{Py} deposited by face-to-face sputtering. The following features prove a good quality of our films: a well-layered structure, complete antiferromagnetic coupling with a low coupling strength (2×10^{-5} J/m^{2} for d_{Cu}=1 nm and 10^{-6} J/m^{^2} for d_{Cu}=2.1 nm) and a low coercive field which make them attractive for possible applications as giant magnetoresistance sensors.
18
Content available remote

Magneto-Optical Study of NiFe/Au/Co/Au Layers

62%
Mazalski P., Postava K., Tekielak M., Maziewski A., Urbaniak M., Szymański B., Stobiecki F.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
369-371
EN
Sputtered NiFe/Au/Co/Au layers with noncollinear magnetizations are of scientific interest for unusual magnetization behavior and their potential application in spintronics. In this paper, we propose to use a material selective sensitivity of magneto-optical Kerr effect for separation of signals from different materials in a bilayer system. The materials selective sensitivity is demonstrated on a sample with two mutually perpendicular Co and NiFe wedges.
19
Content available remote

Influence of Temperature and Annealing on GMR in Sputtered Permalloy/Cu Multilayers

62%
Urbaniak M., Stobiecki F., Luciński T., Kopcewicz M., Grabias A., Aleksiejew J.
Acta Physica Polonica A
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2000
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vol. 97
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issue 3
539-542
EN
The influence of temperature and annealing on giant magnetoresistance of Si(100)/Cu(20 nm)/Py(2 nm)/(Cu(2 nm)/Py(2 nm))_{100} multilayer (Py = Ni_{83}Fe_{17}) sputtered at room temperature in double face-to-face configuration is reported. It was found that giant magnetoresistance value, ΔR_{GMR}/R_{sat} (where R_{sat} is the resistance in saturation), monotonically decreases with increasing temperature (4.5% at 173 K to about 1% at 373 K). This results from the decrease in magnetic change of resistance, ΔR_{GMR}, and to the lesser extent from an increase in R_{sat}, though both of them are caused by the shortening of electrons mean free path. The observed almost linear decrease in giant magnetoresistance saturation field with increasing temperature is explained by temperature changes of magnetization profile. Vibrating sample magnetometer measurements revealed that the increase in temperature results in pronounced decrease in remnant to saturation magnetization ratio (M_{r}/M_{s}) suggesting that at low temperatures magnetic bridges between Py layers play an important role in magnetization process. It is shown that proper annealing, by an annihilation of bridges and/or lateral decoupling, leads to an increase in giant magnetoresistance ratio from 3.4% in as deposited state to 4.7%.
20
Content available remote

Complex Magnetic Structure of Strongly Coupled Fe/Si Multilayers

62%
Dubowik J., Stobiecki F., Szymański B., Kudryavtsev Y., Grabias A., Kopcewicz M.
Acta Physica Polonica A
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2000
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vol. 97
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issue 3
451-454
EN
Fe/Si multilayers with strong bilinear and biquadratic couplings were investigated. A complex structure revealed by the Mössbauer spectroscopy corresponds to multimode ferromagnetic resonance spectra in a non-saturated state. Simple dispersion relations for antiferromagnetic coupled bilayer structures are shown to be inapplicable to the Fe/Si multilayers with a strong biquadratic component to the antiferromagnetic bilinear coupling.
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