Local manipulation and reversal of the exchange bias field by ion irradiation in FeNi/FeMn double layers

Mougin, A.; Mewes, Tim; Jung, Minkyung; Engel, Dieter; Ehresmann, A.; Schmoranzer, H.; Faßbender, J.; Hillebrands, Burkard

doi:10.1103/physrevb.63.060409

Cited by 144 publications

(111 citation statements)

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“…2a, full symbols), consistent with previous work [16]. A discussion of the exchange bias field evolution with ion fluence is given in Ref.…”

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confidence: 71%

“…A discussion of the exchange bias field evolution with ion fluence is given in Ref. [16]. Based upon the latter and ion stopping calculations [17] we note that the interface roughness is not affected when ion fluences are below a few times 10 16 ions/cm 2 .…”

mentioning

confidence: 99%

“…In the present study, polycrystalline bilayers of ferromagnetic Ni 81 Fe 19 and antiferromagnetic Fe 50 Mn 50 were used in order to tailor the exchange bias field by light ion irradiation [15,16]. Bilayers of 10 nm FeMn and 5 nm NiFe were evaporated on a 15 nm thick Cu buffer layer deposited on a thermally oxidized Si substrate.…”

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Probing interface magnetism in the FeMn/NiFe exchange bias system using magnetic second-harmonic generation

et al. 2003

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Second harmonic generation magneto-optic Kerr effect (SHMOKE) experiments, sensitive to buried interfaces, were performed on a polycrystalline NiFe/FeMn bilayer in which areas with different exchange bias fields were prepared using 5 KeV He ion irradiation. Both reversible and irreversible uncompensated spins are found in the antiferromagnetic layer close to the interface with the ferromagnetic layer. The SHMOKE hysteresis loop shows the same exchange bias field as obtained from standard magnetometry. We demonstrate that the exchange bias effect is controlled by pinned uncompensated spins in the antiferromagnetic layer.PACS numbers: 33.55. Fi, 75.30.Gw The magnetic exchange interaction between an antiferromagnetic (AF) and an adjacent ferromagnetic (F) layer may lead to the exchange bias effect discovered in 1956 [1,2]. Among other various intriguing features, this effect leads to a shift of the F hysteresis loop along the field axis by the so-called exchange bias field H eb . For recent reviews see Refs. [3,4,5]. Proposed models to account for the exchange bias involve (i) domain walls or partial domain walls in the AF layer which are either parallel [5,6] or perpendicular [7] to the interface, and/or (ii) uncompensated AF layer magnetic moments at the interface [7,8,9] and/or in the bulk [9,10]. In most exchange bias models, the interfacial uncompensated spins are linked to roughness, structural defects, or disoriented grains. Although uncompensated spins have been already evidenced [11], their behavior during the F layer magnetic reversal has not been reported so far and, experimentally, the relationship between uncompensated spins and exchange bias is still unclear. In the special case where artificial random defects can be introduced in the AF layer (such as in a diluted antiferromagnet), the so-called "domain state model" [9,10] showed that the exchange bias effect stems from the volume AF spin arrangement triggered by non magnetic defects. In this model, AF interfacial reversible and irreversible uncompensated spins (creating M F/AF rev and M AF irr respectively) are distinguished. Some of the interfacial AF uncompensated spins reverse under the action of an external magnetic field and the additional effective interface exchange field originating from the magnetized F layer, whereas the rest of the AF uncompensated spins remain frozen in the same range of applied fields. The reversible uncompensated spins hysteresis loop is found to be shifted along the field axis by H eb and along the magnetization axis by an amount directly proportional to M AF irr , which scales with H eb [10]. Using superconducting quantum interference device magnetometry, this vertical shift of the hysteresis loop of F/AF bilayers has already been measured and related to the exchange bias field sign [12], although its origin was not determined.Here we study the second-harmonic magneto-optic Kerr effect (SHMOKE) in an exchange-bias system. A second-harmonic signal in centrosymmetric materials is selectively generated at their inter...

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“…2a, full symbols), consistent with previous work [16]. A discussion of the exchange bias field evolution with ion fluence is given in Ref.…”

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confidence: 71%

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Probing interface magnetism in the FeMn/NiFe exchange bias system using magnetic second-harmonic generation

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“…2,[6][7][8][9] In addition, dilution and irradiation experiments have shown that the number of defects in the antiferromagnetic layer also influences the domain structure and the exchange bias effect. [20][21][22][23] Since the magnitude of the exchange bias field is directly proportional to the pinned uncompensated moment along the bias direction, magneticfield annealing can change the bias field by modifying the number of pinned spins or realigning the orientation of the spin moment. Thermally activated diffusion changes the number of defects in the IrMn bulk and at CoFe/ IrMn interface during annealing at elevated temperatures.…”

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Influence of the annealing field strength on exchange bias and magnetoresistance of spin valves with IrMn

Kerr

Dijken

Coey

2005

Journal of Applied Physics

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We report on field annealing effects in spin valves with an IrMn pinning layer and spin valves with a synthetic antiferromagnet. The exchange bias field and magnetoresistance of spin valves with an IrMn/ CoFe bilayer at the bottom improve drastically upon annealing in large magnetic fields. The evolution of the exchange bias field with annealing field strength shows a rapid increase up to an applied field of 0.5 T, which is followed by a more gradual improvement up to an annealing field of 5.5 T. The increase of the exchange bias field in large magnetic fields indicates that the interfacial spin structure of the IrMn layer is directly influenced by the annealing field strength.

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“…In the case of ferromagnetic/antiferromagnetic (FM/AFM) exchange-biased bilayers, the exchange bias is sensitive to the interface and the AFM anisotropic energy. Accordingly, ion irradiation has been used to change both the magnitude and direction of the exchange field [9]. The exchange field can be either enhanced by the creation of defects, acting as domain-wall pinning sites, or can be suppressed to zero by the intermixing.…”

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confidence: 99%

Effects of ion-beam irradiation on the L1₀ phase transformation and their magnetic properties of FePt and PtMn films (Invited)

et al. 2005

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In this paper, we illustrate how to modify the structure and magnetic properties of L1 0 FePt and PtMn films using ion-beam irradiation. Highly ordered L1 0 FePt and PtMn phases were achieved directly by using 2 MeV He-ion irradiation without conventional post-annealing. A high ion-beam current density (~µA/cm 2 ) was used to achieve direct beam heating on samples.This irradiation-induced heating process provides efficient microscopic energy transfer and creates excess point defects, which significantly enhances the diffusion and promotes the formation of the ordered L1 0 phase. In-plane coercivity of FePt films greater than 5700 Oe could be obtained after disordered FePt films were irradiated with a He-ion dose of 2.4x10 16 ions/cm 2 . The direct ordering of FePt took place by using ion-irradiation heating at a temperature as low as 230 ℃ . In PtMn-based spin valves, an L1 0 PtMn phase, a large exchange field and a high giant magnetoresistance (GMR) ratio (11%) were simultaneously obtained by using He-ion irradiation. On the other hand, Ge-ion and O-ion irradiation completely destroyed the ferromagnetism of FePt and the GMR of PtMn-based spin valves, respectively.

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Local manipulation and reversal of the exchange bias field by ion irradiation in FeNi/FeMn double layers

Cited by 144 publications

References 22 publications

Probing interface magnetism in the FeMn/NiFe exchange bias system using magnetic second-harmonic generation

Probing interface magnetism in the FeMn/NiFe exchange bias system using magnetic second-harmonic generation

Influence of the annealing field strength on exchange bias and magnetoresistance of spin valves with IrMn

Effects of ion-beam irradiation on the L1₀ phase transformation and their magnetic properties of FePt and PtMn films (Invited)

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Local manipulation and reversal of the exchange bias field by ion irradiation in FeNi/FeMn double layers

Cited by 144 publications

References 22 publications

Probing interface magnetism in the FeMn/NiFe exchange bias system using magnetic second-harmonic generation

Probing interface magnetism in the FeMn/NiFe exchange bias system using magnetic second-harmonic generation

Influence of the annealing field strength on exchange bias and magnetoresistance of spin valves with IrMn

Effects of ion-beam irradiation on the L10 phase transformation and their magnetic properties of FePt and PtMn films (Invited)

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Effects of ion-beam irradiation on the L1₀ phase transformation and their magnetic properties of FePt and PtMn films (Invited)