Effective exchange coupling in permalloy-gadolinium films (original) (raw)
Applied Physics A, 2005
We have studied the influence of the growth conditions on the structural characteristics of sputtered Py(Fe 20 Ni 80)/ Gd/Py(Fe 20 Ni 80) thin films. Auger electron spectroscopy reveals the existence of Ni in the Gd layer. The Ni concentration profile appears asymmetric with a higher concentration close to the top Py layer. This asymmetrical Ni concentration produces a different coercivity of each Py layer. It is possible to reduce the Ni interdiffusion by using multilayers based on Py/Gd bilayers separated by Mo spacers between the Py/Gd bilayers. In these samples we have obtained an enhancement of the structural and magnetic properties.
Domain walls and exchange-interaction in Permalloy/Gd films
New Journal of Physics, 2008
In this work we study the exchange coupling in Permalloy (Py)/gadolinium (Gd) bilayers. The exchange-coupled Py/Gd system is very temperature dependent and moreover the magnetization process in the Py layer is mainly due to domain wall (DW) displacements which are strongly controlled by pinning effects. We propose that this pinning could be caused by magnetostatic and exchange interactions between Py DWs and the magnetostrictive Gd layer. These effects mask the antiferromagnetic coupling between layers and, depending on temperature and Py thicknesses, apparent ferromagnetic coupling occurs. The study has been performed in the 80-300 K temperature range for different Py layer thicknesses and different Py induced anisotropies. Contents 1. Introduction 2 2. Experimental 3 3. Results and discussion 5 4. Conclusions 9 Acknowledgments 9 References 10
Enhanced exchange and reduced magnetization of Gd in an Fe/Gd/Fe trilayer
Physical Review B, 2011
The exchange interaction of Gd adjacent to Fe has been characterized by transport measurements on a double spin valve with a Fe/Gd/Fe trilayer as the middle layer. Our measurements show that the ferromagnetism of the Gd is enhanced by the presence of the Fe, and it remains ferromagnetic over its Curie temperature up to a thickness no smaller than 1 nm adjacent to the Fe. This thickness is more than double what has been reported before. Additionally, the saturation magnetization of the thin Gd layer sandwiched in Fe was found to be half of its bulk value. This reduced magnetization does not seem to be related to the proximity of Fe but rather to the incomplete saturation of Gd even for very high fields.
Enhanced interfacial magnetic coupling of Gd /Fe multilayers
Physical review letters, 2001
The spatial extent zeta(AFM) and strength J(AFM) of the antiferromagnetic (AFM) exchange coupling at buried Gd /Fe interfaces in ferrimagnetic [Gd(50 A)Fe(15,35 A)](15) sputtered multilayers is obtained from combined x-ray resonance magnetic reflectivity and magnetic circular dichroism measurements. zeta(AFM) is 4.1(7) A or approximately 1-2 interatomic distances in bulk Gd and Fe; J(AFM) is 1050(90) K, comparable to the ferromagnetic exchange in bulk Fe.
Physica B: Condensed Matter, 2003
The magnetic coupling between two permalloy layers with a Cr separating layer was studied using LMOKE, polarized neutron reflectivity and XRD. The coupling between two permalloy layers is antiferromagnetic-like when the Cr thickness is near 2.0 nm along the easy axis. A strong biquadratic coupling term has been found from the polarized neutron reflectivity study. The strong biquadratic coupling may be caused by the rough interface between the permalloy and Cr layers. The missing GMR effect of this system might be due to this strong biquadratic coupling of permalloy layers.
Peculiarities of ferrimagnetism of Gd/Co multilayers
Journal of Alloys and Compounds, 2001
The features of the ferrimagnetic ordering in multilayered Gd / Co films have been investigated with a torquemeter, vibrating sample and SQUID magnetometers, and ferromagnetic resonance. A phenomenological analysis of the possible mechanisms of magnetic interaction in these structures was made using the molecular field theory. The model of non-uniform interlayer exchange between Gd and Co layers has some advantages in comparison with the model of partial mixing of the layers.
Magnetic and structural properties of the Gd/Ni-Bilayer-System
Rare earth elements have been the scope of intensive research for many of their different properties over the past decades. The high magnetic permanent moment of these elements aroused a lot of interest and research on their magnetic behavior or structure, which was already conducted in the early 1970s. But due to the challenging problems associated with the handling of rare earths like their strong reactivity with water and oxygen, strong alloying with other metals or their high content of impurities was keeping research only to a small number of involved groups and publications per year. Another issue is the non-epitaxial or even amorphous growth of nearly all rare earth elements if evaporated under UHV conditions. There are only a few substrates which allow an epitaxial growth of gadolinium for example. But still the search for materials with high magnetization or either high or low coercivity for magnetic data storage technology or magnetic sensing elements attract notice to thi...
Magnetic Structures of an Iron–Gadolinium Multilayer at Low Temperatures
Japanese Journal of Applied Physics, 2002
Low-temperature magnetic structures of an [Fe/Gd] 15 multilayer are determined using the resonant X-ray magnetic scattering technique at a synchrotron source. The difference intensities of specular Bragg reflections observed by flipping the helicity of circularly polarized probing X-rays of energy close to the L 3 absorption edge of Gd show that the multilayer is in the Gdaligned state with the magnetic moments of the Gd layers oriented parallel to the applied in-plane field at H ¼ 0:5 kOe, T ¼ 10 K. This transforms into the twisted state with canted Gd moments by raising field strength H and/or temperature T. In the twisted state, the Gd moments at the interfaces and the core of the Gd layers show distinctive canting angles. Temperature and field-dependent in-plane rotations of local Gd moments have been visualized.
Magnetization dynamics in interlayer exchange-coupled in-plane/out-of-plane anisotropy bilayers
Physical Review B, 2009
The static and high-frequency properties of bilayer systems consisting in a single-crystal garnet film with a perpendicular anisotropy exchange coupled with a thin Permalloy film with a small in-plane anisotropy have been investigated both numerically and experimentally. The dynamic susceptibility spectra computed by means of two-dimensional micromagnetic simulations extended to stratified films reveal clearly the existence of multiple resonance lines resulting from the coupling between different magnetic area ͑domain walls, domains͒ inside the garnet film and the Permalloy film. In particular, exaltation of intensive domain wall resonances occurs within the frequency range including the uniform gyromagnetic mode of the Permalloy film. The effect of the garnet and Permalloy film thicknesses on the features of the dynamic susceptibility spectra is then studied. The experimental power absorption spectra recorded on a Permalloy/YIGBiLuAl-like bilayer exhibit well-defined resonance lines, most of them assigned to coupled modes of the bilayer nicely predicted by the micromagnetic simulations. The strong direct exchange coupling at the interface between the two layers appears as a predominant factor for this metal-oxide system.
Physical Review B, 2010
We demonstrate an exchange bias in (Ga,Mn)As induced by antiferromagnetic coupling to a thin overlayer of Fe. Bias fields of up to 240 Oe are observed. Using element-specific x-ray magnetic circular dichroism measurements, we distinguish a strongly exchange coupled (Ga,Mn)As interface layer in addition to the biassed bulk of the (Ga,Mn)As film. The interface layer remains polarized at room temperature. PACS numbers: 75.70.Cn, 75.50.Pp, 75.50.Bb Ferromagnetic (FM) semiconductors offer the prospect of combining high-density storage and gate-controlled logic in a single material. The realization of spin-valve devices from FM semiconductors requires the controlled switching of magnetization in adjacent layers between antiferromagnetic (AFM) and FM configurations. This has motivated several theoretical investigations of interlayer coupling in all-semiconductor devices 1 , and AFM coupling has recently been demonstrated in (Ga,Mn)As multilayers separated by p-type non-magnetic spacers 2 . However, the Curie temperature T C of (Ga,Mn)As is currently limited to 185 K in single layers 3 , and is typically much lower for layers embedded within a heterostructure 2 , which is an obstacle to the practical implementation of semiconductor spintronics.
Temperature dependence of ferromagnetic resonance in permalloy/NiO exchange-biased films
The European Physical Journal B, 2005
The temperature dependencies of the ferromagnetic resonance (FMR) linewidth and the resonance field-shift have been investigated for NiO/NiFe exchange-biased bilayers from 78 K to 450 K. A broad maximum in the linewidth of 500 Oe, solely due to the exchange-bias, is observed at ≈150 K when the magnetic field is applied along the film plane. When the magnetic field is applied perpendicular to the film plane, the maximum in the linewidth is less pronounced and amounts to 100 Oe at the same temperature. Such a behavior of the FMR linewidth is accompanied with a monotonic increase in the negative resonance field-shift with decreasing temperature. Our results are compared with the previous experimental FMR and Brillouin light scattering data for various ferromagnetic/antiferromagnetic (FM/AF) structures, and suggest that spin dynamics (spin-wave damping and anomalous resonance field-shift) in the FM/AF structures can be described in a consistent way by a single mechanism of the so-called slow-relaxation.
Exchange interactions in Fe/Y multilayers
Journal of Alloys and Compounds, 2005
The magnetization of Fe/Y multilayers has been measured as a function of temperature. A bulk-like T 3/2 temperature dependence of the magnetization is observed for all multilayers in the temperature range 5-300 K. The spin-wave constant B is found to decrease inversely with t Fe. A simple theoretical model with exchange interactions only, and with non-interacting magnons, has been used to explain the temperature dependence of the magnetization and the approximate values for the bulk exchange interaction J b , surface exchange interaction J s and the interlayer exchange interaction J I for various Fe layer thicknesses have been obtained.
Magnetic field-induced spin reorientation in gadolinium surface layer of Gd/Fe multilayers
Journal of Magnetism and Magnetic Materials, 1998
Magnetization processes in thin Gd/Fe multilayer films have been studied by means of the longitudinal magnetooptical Kerr effect and magnetization measurements. Comparison between magneto-optical and magnetic measurements allows one to conclude that a field-induced surface spin reorientation occurs in the studied films for a magnetic field applied in the film plane. The experimental results can be satisfactorily interpreted in the framework of the developed theoretical model. This model predicts a formation of a noncollinear magnetic structure within the gadolinium surface layer during the process of the field-induced spin reorientation phase transition.
Ferromagnetic resonance studies of exchange coupled ultrathin Py/Cr/Py trilayers
Journal of Applied Physics, 2010
Magnetic properties of ultrathin Py/Cr/Py trilayers have been investigated as a function of Cr spacer layer thickness by using ferromagnetic resonance ͑FMR͒ and vibrating sample magnetometer ͑VSM͒ techniques. The Cr spacer layer thickness was increased from 4 to 40 Å with 1 Å steps to determine the dependence of interlayer exchange coupling between ferromagnetic layers on the spacer layer thickness. Two strong and well resolved peaks were observed which correspond to a strong ͑acoustic͒ and weak ͑optic͒ modes of magnetization precession in the effective dc field due to the exciting external microwave field as the external dc field orientation comes close to the film normal. The separation of the two modes in the field axis depends on the thickness of Cr spacer layer. An interchange in the relative positions of the acoustic and optic modes has been observed for a particular thickness of Cr spacer layer as well. A computer program for magnetically exchange coupled N magnetic layers was written to simulate the experimental FMR spectra and to obtain the magnetic parameters of ultrathin Py/Cr/Py trilayers. FMR data have been analyzed from every aspect by using this program and interlayer exchange coupling constant was calculated for the prepared structures. It was found that the relative position of the peaks depends on the nature ͑sign͒ of the interlayer exchange coupling between ferromagnetic layers through Cr spacer layer. In Py/Cr/Py trilayers, strength of the interlayer exchange coupling constant oscillates and changes its sign with Cr spacer layer thickness with a period of about 11 Å.
Scientific Reports
We demonstrate the magnetically-induced transparency (MIT) effect in Y$$_3$$3Fe$$_5$$5O$$_{12}$$12(YIG)/Permalloy (Py) coupled bilayers. The measurement is achieved via a heterodyne detection of the coupled magnetization dynamics using a single wavelength that probes the magneto-optical Kerr and Faraday effects of Py and YIG, respectively. Clear features of the MIT effect are evident from the deeply modulated ferromagnetic resonance of Py due to the perpendicular-standing-spin-wave of YIG. We develop a phenomenological model that nicely reproduces the experimental results including the induced amplitude and phase evolution caused by the magnon–magnon coupling. Our work offers a new route towards studying phase-resolved spin dynamics and hybrid magnonic systems.
Effect of temperature on the exchange bias in FeMn/X/Fe20Ni80 (X = Ta, Gd) films
Journal of Physics: Conference Series, 2019
The influence of temperature on the exchange bias in the Fe50Mn50/X/Fe20Ni80 (X = Ta, Gd) films was investigated. It is shown that in the film structures without a spacer between FeMn and permalloy layers, the temperature dependence of the value of the exchange bias field is non-monotonous. The introduction of an ultrathin spacer leads not only to a change in the magnitude of the interlayer exchange coupling, but also to a change in the behavior of its temperature dependence.
Magnetic properties of epitaxial gadolinium hydride films
Journal of Alloys and Compounds, 2002
Epitaxial gadolinium films were synthesized by pulsed laser deposition on a molybdenum layer itself grown on a sapphire substrate. These films exhibit high structural order, as shown by RHEED and X-ray diffraction. The structure of hydrogenated films were also studied. The magnetic properties of gadolinium and gadolinium hydride were measured in a vibrating sample magnetometer at temperatures ranging from 10 K to room temperature. Unexpectedly, films hydrogenated at 0.5 MPa for 30 min remain partly ferromagnetic.
Tailoring interface mixing and magnetostriction in Permalloy/Pt multilayers
arXiv: Materials Science, 2020
We present deposition of multilayers consisting of 20 repetitions of 15 A permalloy Ni$_{80}$Fe$_{20}$ at.% (Py) and 5 AAA Pt. We studied the effect of substrate roughness and sputtering power on the in-plane magnetic uniaxial anisotropy of the film. We also used different methods of dc magnetron sputtering (dcMS) and high power impulse magnetron sputtering (HiPIMS) for deposition of Py. The multilayers were characterized by X-ray reflectivity and diffraction as well as magneto-optical Kerr effect (MOKE). It is shown that HiPIMS presents multilayers with unique surface and interface roughness that is also present for the substrate with higher surface roughness. Multilayers prepared by both dcMS and HiPIMS present a strong (111) texture normal to the film plane. The results show that utilizing HiPIMS leads to a minimum interface mixing between individual layers compared to dcMS at different powers. This is associated with limited Pt displacement due to its mass as well smooth surface...
Influence of the Fe content on the Gd magnetic ordering temperature in Ni1−xFex/Gd multilayers
Physical Review B, 2012
We explore the influence of Fe content on the interfacial magnetic properties of Ni 1−x Fe x (50Å)/Fe (tÅ)/ Gd(50Å)/Fe (tÅ)/Ni 1−x Fe x (50Å) (x = 0.2 and 0.6, and t = 0 and 10Å) multilayers by means of element-specific x-ray magnetic circular dichroism measurements at Gd M 5 and (Ni, Fe) L 2,3 absorption edges, superconducting quantum interference device magnetometry, and specular reflectivity measurements. Increasing Fe content in the Ni-Fe layer enhances the Gd ordering temperature in the interfacial regions. Addition of a 1-nm Fe spacer results in the largest enhancement in Gd ordering temperature in both interior and interfacial Gd regions, even for high Ni content in the Ni-Fe layer. This indicates that the Fe spacers act as effective barriers (albeit imperfect) in reducing Gd-Ni contact interactions responsible for limiting the interfacial Gd magnetic ordering temperature to values larger than bulk Gd, but significantly lower than observed at Fe/Gd interfaces.
Evaluation of interlayer exchange coupling in α-Fe(100)/Nd2Fe14B(001) films
Journal of the Korean Physical Society, 2013
We fabricated ↵-Fe(100)/Nd2Fe14B(001) bilayer films with di↵erent thicknesses values of the ↵-Fe layer on MgO(100) substrates by using an ultra-high-vacuum (UHV) magnetron sputtering system. The exchange coupling constant at the heterointerfaces of ↵-Fe(100)/Nd2Fe14B(001) was evaluated by analyzing the magnetization curves and the ferromagnetic resonance (FMR) spectra. We observed a significant lower shift of the ↵-Fe resonance field compared to that of the ↵-Fe single layer irrespective of the Fe-layer thickness, which suggests the existence of an internal field owing to a positive exchange coupling between the ↵-Fe(100) and the Nd2Fe14B(001) layers.