Asymmetric magnetization reversal in exchange‐biased Co/Pt multilayers

Dijken, Sebastiaan van; Czapkiewicz, M.; Żołądź, M.; Stobiecki, T.

doi:10.1002/pssb.200562498

Cited by 13 publications

(9 citation statements)

References 14 publications

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“…We can easily see that the loop is not symmetrical, and at its backward path is not back-saturated to the starting +1 value for the applied field H = 5. This asymmetry represented by the loop shape factor is similar to that described by S. van Dijken et al [1] and tested experimentally for different non-magnetic spacers in the (Co/Pt) n /IrMn structures. They measured a negative perpendicular anisotropy contribution from the Co/IrMn interface (-0.09 mJ/m 3 ) that weakened the perpendicular exchange bias.…”

Section: Simulationssupporting

confidence: 76%

“…Fig. 3 provides normalized values of the exchange bias, the coercivity, the loop shape factor, the magnetization of minority spins biased in the direction opposite to the expected bias, and the magnetization of majority spins pinned in the expected exchange-bias direction as a function of the surface coverage p. As seen in this figure, the exchange bias is fully correlated with the number of majority spins, while the number of minority spins follows the loop shape factor, and falls into the two minima: N (1) op (min) and N (2) op(min) . The latter unexpected result may have important implications for real magnetoelectronic devices.…”

Section: Discussionmentioning

confidence: 79%

“…This effect, known as the perpendicular exchange bias (EB), can also be controlled by cooling from temperatures above the Néel AFM temperature T N in an external magnetic field oriented perpendicular to the direction of the structure surface [1]. The exchange bias phenomenon results mainly from short range interactions between FM and AFM spins.…”

Section: Introductionmentioning

confidence: 99%

“…First, for some layered systems the two types of FM biased domains have been observed, namely the minority domains that were biased in the direction opposite to the preferred exchange-bias direction, and the majority domains that followed the exchange bias [1]. The occurrence of minority domains was explained as a consequence of the deposition method, especially as the result of a stray fields disturbance produced by magnetron guns.…”

Section: Introductionmentioning

confidence: 99%

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Simulating a perpendicular exchange-biased structure with a partially covering nonmagnetic insertion at the FM/AFM interface

Błlachowicz

2006

Open Physics

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Abstract:The existence of minority spins, opposite to the perpendicular exchange bias, and majority spins aligned with this bias, and the dependence of the perpendicular exchange-bias field on the imprint effect, caused by the partially covering spacer at the ferromagnetic/antiferromagnetic (FM/AFM) interface, have been studied using Ising-type simulations. The present investigation suggests that the main factors influencing this phenomenon were dependent on the FM/AFM interface morphology, the balance between FM/AFM coupling and the FM-spins coupling, and the numerical balance between minority and majority spins. It was also determined that the imprint phenomenon can be used to enhance the perpendicular exchange-bias for small partial insertions at the FM/AFM interface.

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Section: Simulationssupporting

confidence: 76%

Section: Discussionmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simulating a perpendicular exchange-biased structure with a partially covering nonmagnetic insertion at the FM/AFM interface

Błlachowicz

2006

Open Physics

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“…This effect is due to stray fields originating from the magnetron guns whose net out-of-plane component ͑Ϸ2.5 mT͒ favors one perpendicular magnetization state over the other. 22 Magnetic force microscopy ͑MFM͒ was used to image the exchange biased 320 nm caps at room temperature. As shown in Fig.…”

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confidence: 99%

Size-dependent scaling of perpendicular exchange bias in magnetic nanostructures

et al. 2007

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Size-dependent scaling is studied in exchange biased nanostructures obtained by depositing ͓Pt/ Co͔ 3 / IrMn multilayers with perpendicular magnetization onto an array of monodisperse polystyrene nanospheres with a diameter ranging from 58 nm to 320 nm. We find that the exchange bias field increases with the inverse of the sphere diameter when the IrMn layer is single domain. This scaling behavior, which is favorable for further miniaturization of magnetic devices, can be understood within the context of a random field model by a statistical distribution of Mn spins at the Co/ IrMn interface. DOI: 10.1103/PhysRevB.75.012413 PACS number͑s͒: 75.50.Ee, 61.46.Df, 75.70.Ϫi, 75.75.ϩa Fifty years ago, Meiklejohn and Bean discovered a new form of magnetic anisotropy.1 Their discovery, called exchange bias, was a unidirectional shift of the hysteresis loop along the magnetic field axis for ferromagnetic ͑FM͒ materials in close contact with an antiferromagnet ͑AFM͒. Due to its technological applications, exchange bias coupling has generated intense experimental 2 and theoretical research efforts.3-7 Nowadays, FM/AFM bilayers are incorporated in magnetic thin film devices such as magnetic spin-valve sensors, magnetic tunnel junction read heads for hard-disk drives, and magnetic random access memories. For continuous FM/AFM bilayers, variations of the exchange bias field with AFM grain size, 5 AFM domain size, 8 and AFM film thickness 9-11 have been measured, illustrating the theoretically predicted importance of the AFM domain size.Although there are many reports on exchange biased nanostructures, 12-16 mainly with a ferromagnetic in-plane easy axis, very few of them address in depth the effects of miniaturization on the exchange bias properties, where unique effects will set in at some critical length scales; and even the trends are controversial. While most of the nanosystems exhibit a decrease in exchange bias with size reduction, it has been recently reported for sub-100 nm NiFe-IrMn square dots, that depending on the thickness of the AFM layer, the dots could either have larger or smaller bias field than the respective continuous films.14 In addition, many studies focus on structures with dimensions larger than the AFM domain size or compare properties of single-size nanostructures with those of continuous films. Hence, a detailed understanding of size-dependent scaling of exchange bias in magnetic nanostructures that confine the AFM to a singledomain state is still lacking.Here, we present a conclusive account of the effects of size reduction on exchange bias. In our experiments we use an original self-assembly method to systematically vary the FM/AFM structure size and AFM layer thickness. Measurements on these structures reveal a statistical enhancement of the exchange bias field in magnetic nanostructures. This enhancement, which is explained within the context of a random field model, follows a simple scaling law.To fabricate the nanostructures, we employed dense arrays of monodisperse spherical polystyrene p...

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Asymmetric Manipulation of Perpendicular Exchange Bias and Programmable Spin Logical Cells by Spin–Orbit Torque in a Ferromagnet/Antiferromagnet System

Guo,

Shi,

Wang

et al. 2024

Advanced Science

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Antiferromagnets are competitive candidates for the next generation of spintronic devices owing to their superiority in small‐scale and low‐power‐consumption devices. The electrical manipulation of the magnetization and exchange bias (EB) driven by spin‐orbit torque (SOT) in ferromagnetic (FM)/antiferromagnetic (AFM) systems has become focused in spintronics. Here, the realization of a large perpendicular EB field in Co/IrMn and the effective manipulation of the magnetic moments of the magnetic Co layer and EB field by SOT in Pt/Co/IrMn system is reported. During the SOT‐driven switching process, an asymmetrically manipulated state is observed. Current pulses with the same amplitude but opposite directions induce different magnetization states. Magneto–optical Kerr measurements reveal that this is due to the coexistence of stable and metastable antiferromagnetic domains in the AFM. Exploiting the asymmetric properties of these FM/AFM structures, five spin logic gates, namely AND, OR, NOR, NAND, and NOT, are realized in a single cell via SOT. This study provides an insight into the special ability of SOT on AFMs and also paves an avenue to construct the logic‐in‐memory and neuromorphic computing cells based on the AFM spintronic system.

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Asymmetric magnetization reversal in exchange‐biased Co/Pt multilayers

Cited by 13 publications

References 14 publications

Simulating a perpendicular exchange-biased structure with a partially covering nonmagnetic insertion at the FM/AFM interface

Simulating a perpendicular exchange-biased structure with a partially covering nonmagnetic insertion at the FM/AFM interface

Size-dependent scaling of perpendicular exchange bias in magnetic nanostructures

Asymmetric Manipulation of Perpendicular Exchange Bias and Programmable Spin Logical Cells by Spin–Orbit Torque in a Ferromagnet/Antiferromagnet System

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