Magnetic properties of uniaxial synthetic antiferromagnetic films (original) (raw)
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Magnetic properties of uniaxial synthetic antiferromagnets for spin-valve applications
Physical Review B, 2005
The magnetic properties of synthetic antiferromagnetic Si͑100͒ /Ta ͑5 nm͒ /Co͑t 1 ͒ / Ru ͑0.65 nm͒ /Co͑t 2 ͒ /Ta ͑10 nm͒ with an obliquely sputtered Ta underlayer are reported as a function of the top Co layer thickness, t 2 . The morphological origin of the large in-plane magnetic anisotropy created by the obliquely sputtered Ta underlayer is revealed by atomic force microscopy. The magnetic anisotropy of the base Co layer is determined by measuring the dispersion of the Damon-Eshbach spin-wave mode with Brillouin light scattering. Ferromagnetic resonance measurements and hysteresis loops reveal that both the anisotropy and the saturation field of the trilayer system decrease with increasing top Co layer thickness. The dependence of the saturation field on layer thickness is fitted to an energy minimization equation that contains both bilinear and biquadratic exchange coupling constants. Magnetoresistance and polarized neutron reflectometry results both confirm that the magnetic reversal process of the system is through magnetic domain formation followed by rotation.
IEEE Transactions on Magnetics, 2007
We investigated biquadratic exchange coupling strength in sputtered uniaxial antiferromagnetic Co/Ru/Co trilayers, which can be tuned by applying a magnetic field perpendicular to the sample surface during deposition. The perpendicular field induces a columnar grain structure that results in a perpendicular magnetic anisotropy for single Co layers. The perpendicular magnetic anisotropy is detected by combined magnetization and Brillouin light scattering measurements. In trilayers, increasing the perpendicular field during deposition results in a monotonic increase of the biquadratic exchange coupling strength, so these samples provide an experimental realization of the effect of variable biquadratic coupling strength on magnetic hysteresis behavior. The hard-axis remanence is a direct measure of biquadratic exchange coupling strength, which we demonstrated both by experiment and by a Stoner-Wohlfarth model that includes the relevant magnetic parameters.
JOM, 2022
Ferromagnetic (FM) layers separated by nonmagnetic metallic spacer layers can exhibit Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling which may lead to a stable synthetic antiferromagnetic (SAF) phase. In this article we study magnetization reversal in [Co/Pt] layers by varying the number of bilayer stacks (Pt/Co) as well as thickness of Ir space layer t Ir on rigid Si(100) and flexible polyimide substrates. The samples with t Ir = 1.0 nm shows a FM coupling whereas samples with t Ir = 1.5 nm shows an AFM coupling between the FM layers. At t Ir = 2.0 nm, it shows a bow-tie shaped hysteresis loop indicating a canting of magnetization at the reversal. Higher anisotropy energy as compared to the interlayer exchange coupling (IEC) energy is an indication of the smaller relative angle between the magnetization of lower and upper FM layers. We have also demonstrated the strain induced modification of IEC as well as magnetization reversal phenomena. The IEC shows a slight decrease upon application of compressive strain and increase upon application of tensile strain which indicates the potential of SAFs in flexible spintronics.
Three-dimensional spin structure in exchange-biased antiferromagnetic/ferromagnetic thin films
Applied Physics Letters, 2009
A coexistence of lateral and in-depth domain walls in antiferromagnet/ferromagnet ͑AF/FM͒ thin films exhibiting double hysteresis loops ͑DHLs͒ is demonstrated. Comparison of single and DHLs together with local and global measurements confirms the formation of two oppositely oriented domains in the AF that imprint a lateral domain structure into the FM layer. Most significantly, the magnetization reversal mechanism within each opposite domain takes place by incoherent rotation of spring-like domain walls extending through the Ni thickness. Therefore, complex three-dimensional domain walls are created perpendicular and parallel to the AF/FM interface in exchange biased systems.
Physical Review B, 2016
This study demonstrates the effect of antiferromagnet-induced perpendicular magnetic anisotropy (PMA) on ferromagnetic/antiferromagnetic/ferromagnetic (FM/AFM/FM) trilayers and reveals its interplay with a longrange interlayer coupling between separated FM layers. In epitaxially grown 12 monolayer (ML) Ni/Co/Mn/5 ML Co/Cu(001) films, magnetic hysteresis loops and element-resolved magnetic domain imaging showed that the magnetization direction of the top layers of 12 ML Ni/Co films could be changed from the in-plane direction to the perpendicular direction, when the thickness of the Mn films (t Mn) was greater than a critical value close to the thickness threshold associated with the onset of AFM ordering (t Mn = 3.5 ML). The top FM layers exhibited a significantly enhanced PMA when t Mn increased further, and this enhancement can be attributed to a strengthened AFM ordering of the volume moments of the Mn films, as evidenced by the presence of induced domain frustration. By contrast, the long-range interlayer coupling presented clear effects only when t Mn was at a lower coverage.
Chinese Physics B, 2012
The magnetic anisotropy and magnetization reversal of single crystal Fe films with thickness of 45 monolayer (ML) grown on Si(111) have been investigated by ferromagnetic resonance (FMR) and vibrating sample magnetometer (VSM). Owing to the significant modification of the energy surface in remanent state by slight misorientation from (111) plane and a uniaxial magnetic anisotropy, the azimuthal angular dependence of in-plane resonance field shows a six-fold symmetry with a weak uniaxial contribution, while the remanence of hysteresis loops displays a two-fold one. The competition between the first and second magnetocrystalline anisotropies may result in the switching of in-plane easy axis of the system. Combining the FMR and VSM measurements, the magnetization reversal mechanism has also been determined.
Field-driven reorientation in ultrathin ferromagnetic films with uniaxial anisotropy
2000
The field-driven spin reorientation transition in uniaxial in-plane magnetized films is discussed by means of phase diagrams which are obtained from the stability analysis of the thermodynamical potential. A classification of the field induced reorientation is carried out concerning the anisotropy axes in films grown on vicinal and twofold low-index surfaces. It is shown that hard-axis loops with magnetization flop are directly related to the reorientation in field. In the framework of the general theory the hard-axis loops can be precisely analyzed.
Reversible susceptibility studies of magnetization switching in FeCoB synthetic antiferromagnets
Journal of Applied Physics, 2007
In this paper we present a study of switching characteristics of a series of synthetic antiferromagnet ͑SAF͒ structures using reversible susceptibility experiments. Three series of SAF samples were considered in our study with ͑t1, t2͒, the thickness of the FeCoB layers of ͑80 nm, 80 nm͒, ͑50 nm, 50 nm͒, and ͑80 nm, 20 nm͒ and with the interlayer of Ru ranging from 0 to 2 nm. A vector vibrating sample magnetometer was used to measure the hysteresis loops along the different directions in the plane of the samples. The reversible susceptibility experiments were performed using a resonant method based on a tunnel diode oscillator. We showed that the switching peaks in the susceptibility versus field plots obtained for different orientations of the applied dc field can be used to construct the switching diagram of the SAF structure. The critical curve constitutes the fingerprint of the switching behavior and provides information about micromagnetic and structural properties of SAF which is an essential component of modern magnetic random access memories.
Physical Review B, 2017
We report the magnetotransport properties of ferromagnet (FM)/antiferromagnet (AFM) Fe2CrSi/Ru2MnGe epitaxial bilayers using current-in-plane configurations. Above the critical thickness of the Ru2MnGe layer to induce exchange bias, symmetric and asymmetric curves were observed in response to the direction of FM magnetocrystalline anisotropy. Because each magnetoresistance curve showed full and partial AFM rotation, the magnetoresistance curves imply the impact of the Fe2CrSi magnetocrystalline anisotropy to govern the AFM rotation. The maximum magnitude of the angular-dependent resistance-change ratio of the bilayers is more than an order of magnitude larger than that of single-layer Fe2CrSi films, resulting from the reorientation of AFM spins via the FM rotation. These results highlight the essential role of controlling the AFM rotation and reveal a facile approach to detect the AFM moment even in current-in-plane configurations in FM/AFM bilayers.