Temperature dependence of the pinning field and coercivity of NiFe layers coupled with an antiferromagnetic FeMn layer

Fujiwara, Hideo; Nishioka, K.; Hou, C.; Parker, M.R.; Gangopadhyay, S.; Metzger, Robert D.

doi:10.1063/1.362039

Cited by 39 publications

(16 citation statements)

References 9 publications

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“…This asymmetry results in a reduction of the exchange bias. Our results are in good qualitative agreement with experimental ones [22][23][24][25][26], where an exchange bias was not found in the Fe/FeF 2 (100) system even though the FeF 2 (100) orientation possesses uncompensated spins at the interface. Therefore, domain wall formation in AFM systems is a good candidate to explain the zero exchange bias in experiments.…”

Section: Resultssupporting

confidence: 81%

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Effect of Interface Roughness on Exchange Bias of an Uncompensated Interface: Monte Carlo Simulation

Li¹,

Moon²,

Lee³

2011

Journal of Magnetics

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By means of Monte Carlo simulation, we investigate the effects of interface roughness and temperature on the exchange bias and coercivity in ferromagnetic (FM)/antiferromagnetic (AFM) bilayers. Both exchange bias and coercivity are strongly dependent on interface roughness. For a perfect uncompensated interface a domain wall is formed in the AFM system during FM reversal, which results in a very small exchange bias. However, a finite interface roughness leads to a finite value of the exchange bias due to the existence of pinned spins at the AFM surface adjacent to the mixed interface. It is observed that the exchange bias decreases with increasing temperature, consistent with the experimental results. It is also observed that a bump in coercivity occurs around the blocking temperature.

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Section: Resultssupporting

confidence: 81%

“…This is evidence that blocking temperature is partly related to interface roughness. Interestingly, a peak of coercivity occurs at the so-called blocking temperature when the exchange bias field becomes zero, qualitatively consistent with experimental results [22][23][24][25][26]. Fig.…”

Section: Resultssupporting

confidence: 77%

Effect of Interface Roughness on Exchange Bias of an Uncompensated Interface: Monte Carlo Simulation

Li¹,

Moon²,

Lee³

2011

Journal of Magnetics

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“…The temperature dependence of H C for ZnF 2 ͞Fe͞Al, also in It is interesting that in both cases the H C enhancement below T N does not saturate at low temperatures, despite the fact that H E reaches a temperature independent value (presumably this reflects the saturation of the AF sublattice magnetization and anisotropy [13]). Such behavior in H E and H C has been observed in several systems (e.g., [4][5][6][14][15][16]) and appears to be a common phenomenon. It seems clear that this behavior warrants further study.…”

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confidence: 98%

Coercivity Enhancement in Exchange Biased Systems Driven by Interfacial Magnetic Frustration

et al. 2000

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We report the temperature and cooling field dependence of the coercivity of exchange biased MnF 2 ͞Fe bilayers. When the antiferromagnetic surface is in a state of maximum magnetic frustration and the net exchange bias is zero, we observe a strong enhancement of the coercivity, which is proportional to the exchange coupling between the layers. Hence, the coercivity can be tuned in a reproducible and repeatable fashion in the same sample. We propose that a frustrated interface provides local energy minima which effectively pin the propagating domain walls in the ferromagnet, leading to an enhanced coercivity. PACS numbers: 75.70.Cn, 75.30.Gw The magnetic coercivity H C (i.e., the half-width of the magnetic hysteresis loop) is an important parameter used to characterize magnetic materials. Control over the coercivity is desirable to tune the behavior of magnetic devices. In spite of this, the issue of controlling the magnetic coercivity has received little attention from physicists as it is supposed to be an extrinsic quantity often determined by such parameters as defect density. As such it is difficult to control in a reproducible fashion by changing an external parameter. Exchange bias H E (the shift of the hysteresis loop along the field axis) has been extensively studied in antiferromagnetic (AF)/ferromagnetic (F) bilayers, although a quantitative understanding is still unavailable [1]. Despite this, some intriguing correlations exist between H E and H C . Moreover, recent theoretical work [2,3] claims that the behavior of H C and the correlations between H E and H C provide important clues as to the microscopic origin of exchange anisotropy. However, experimental investigations of H C , as well as H E , in systems with well controlled and characterized microstructure are rare ([4-7] are examples).Here we present measurements on an exchange biased system in which the coercivity can be tuned by the field applied ͑H FC ͒ when cooling through the AF Néel temperature T N . In this fashion, the AF surface spin structure can be varied and its effect on the behavior of H E and H C observed. The crossover from negative to positive H E , with increasing H FC , is accompanied by an additional increase in the coercivity. This increase is in addition to that which occurs on cooling below T N and increases with the exchange coupling between the AF and F layers. The dependence of the exchange bias on cooling field and temperature can be analyzed using a simple model in which the AF surface spin structure is modified by the applied H FC , in the presence of an antiferromagnetic coupling between the F and AF layers [7][8][9]. We show that this enhancement is brought about by magnetic frustration at the AF͞F interface, a result that has important implications for the physics of exchange biased systems. 27 Torr. X-ray diffraction, grazing incidence reflectivity, and reflection high energy electron diffraction were used for structural characterization, while magnetic measurements were made with a SQUID magnetometer between...

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“…[293]) and H e and T B are sizedependent, which is emphasized in this section. Besides, H e and T B are also functions of AFM orientation (compensated versus uncompensated AFM surface [298][299][300][301][302][303] and in-plane versus out-of-plane AFM spins [298,299,302]), of FM/AFM interface disorder (roughness [299,301,302,[304][305][306], crystallinity [307,308], grain size [309,310], of interface impurity layers [311]), and of strain effect [312][313][314], of stoichiometry [293] or of presence of multiple phases [315] and so forth.…”

Section: Exchange Bias In Fm/afm Heterostruc-turesmentioning

confidence: 99%

Size Dependence of Structures and Properties of Magnetic Materials

Jiang¹,

Lang²

2007

TONANOJ

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Due to the involvement of high portion of atomic coordination imperfection in surfaces and interfaces, the properties of magnetic nanocrystals dramatically differ from that of the corresponding bulk counterparts, which have led to a surge in both experimental and theoretical investigations in the past decades. This review summarizes the studies for these size-dependent magnetic properties, and additional thermal or phase stabilities, and mechanical properties. To interpret the above phenomena, a thermodynamic model for the size dependence and interface dependences of these properties is described, which is based on Lindemann s criterion for melting, Mott s expression for the vibrational melting entropy, and Shi s model for the size-dependent melting temperature. The model without any adjustable parameter is confirmed by a large number of experimental results, and helps us to understand the structures and properties of the magnetic nanocrystals. Moreover, other theoretical works on the above properties are also mentioned and commented.

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Temperature dependence of the pinning field and coercivity of NiFe layers coupled with an antiferromagnetic FeMn layer

Cited by 39 publications

References 9 publications

Effect of Interface Roughness on Exchange Bias of an Uncompensated Interface: Monte Carlo Simulation

Effect of Interface Roughness on Exchange Bias of an Uncompensated Interface: Monte Carlo Simulation

Coercivity Enhancement in Exchange Biased Systems Driven by Interfacial Magnetic Frustration

Size Dependence of Structures and Properties of Magnetic Materials

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