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Cooling field and temperature dependent exchange bias in spin glass/ferromagnet bilayers.

Rui WB, Hu Y, Du A, You B, Xiao MW, Zhang W, Zhou SM, Du J - Sci Rep (2015)

Bottom Line: Significantly, increasing in the magnitude of HFC reduces (increases) the value of HE in the negative (positive) region, resulting in the entire HE∼T curve to move leftwards and upwards.In the meanwhile, HFC variation has weak effects on HC.Thus this work reveals that the SG/FM bilayer system containing intimately coupled interface, instead of a single SG layer, is responsible for the novel EB properties.

View Article: PubMed Central - PubMed

Affiliation: National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P. R. China.

ABSTRACT
We report on the experimental and theoretical studies of cooling field (HFC) and temperature (T) dependent exchange bias (EB) in FexAu1-x/Fe19Ni81 spin glass (SG)/ferromagnet (FM) bilayers. When x varies from 8% to 14% in the FexAu1-x SG alloys, with increasing T, a sign-changeable exchange bias field (HE) together with a unimodal distribution of coercivity (HC) are observed. Significantly, increasing in the magnitude of HFC reduces (increases) the value of HE in the negative (positive) region, resulting in the entire HE∼T curve to move leftwards and upwards. In the meanwhile, HFC variation has weak effects on HC. By Monte Carlo simulation using a SG/FM vector model, we are able to reproduce such HE dependences on T and HFC for the SG/FM system. Thus this work reveals that the SG/FM bilayer system containing intimately coupled interface, instead of a single SG layer, is responsible for the novel EB properties.

No MeSH data available.


Related in: MedlinePlus

The M-H hysteresis loops measured for a Fe11Au89(50 nm)/FeNi(5 nm) sample in the temperature range of 2 K–7 K (a) and 8 K–20 K (b).The arrows are guides to eyes, indicating the direction of loop shift.
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f2: The M-H hysteresis loops measured for a Fe11Au89(50 nm)/FeNi(5 nm) sample in the temperature range of 2 K–7 K (a) and 8 K–20 K (b).The arrows are guides to eyes, indicating the direction of loop shift.

Mentions: Figure 1 unambiguously demonstrates that for the SG/FM bilayers the HE ∼ T curve depends strongly on the composition of the SG layer. Previously, such sign-changeable behavior of HE against T was explained by the competition between long-range oscillatory RKKY couplings from the spins deep inside the SG layer and those close to the interface2122. In the present work, besides reconsidering the sign-changeable behavior, we focus on studying the HE and HC influenced by HFC. First we discuss the evolution of M-H hysteresis loops versus T. Figure 2 shows the M-H hysteresis loops obtained between 2 K and 20 K for the Ta(4 nm)/Fe11Au89(50 nm)/FeNi(5 nm)/Ta(2 nm) sample, after cooled from 300 K to 2 K under HFC = 50 kOe. The M-H hysteresis loop measured at 2 K clearly shows that a negative EB was established after field cooling. As shown in Fig. 2(a), when T increases from 2 K to 7 K, the ascending branch of the hysteresis loop shifts rightwards while the descending branch keeps almost unchanged. With further increasing in T from 8 K to 20 K, as displayed in Fig. 2(b), the hysteresis loop shrinks from both sides towards the center but the shift of ascending branch is more significantly than the descending branch. Therefore, the different T-dependent variation behaviors of the two loop branches lead to the concurrent peak on both the HE ∼ T and HC ∼ T curves, coinciding with the appearance of TP ∼ 7 K as shown in Fig. 1. These results indicate that the T-dependent magnetization reversal mechanisms and/or the thermodynamic spin relaxation at the descending and ascending branches may be quite different.


Cooling field and temperature dependent exchange bias in spin glass/ferromagnet bilayers.

Rui WB, Hu Y, Du A, You B, Xiao MW, Zhang W, Zhou SM, Du J - Sci Rep (2015)

The M-H hysteresis loops measured for a Fe11Au89(50 nm)/FeNi(5 nm) sample in the temperature range of 2 K–7 K (a) and 8 K–20 K (b).The arrows are guides to eyes, indicating the direction of loop shift.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4562234&req=5

f2: The M-H hysteresis loops measured for a Fe11Au89(50 nm)/FeNi(5 nm) sample in the temperature range of 2 K–7 K (a) and 8 K–20 K (b).The arrows are guides to eyes, indicating the direction of loop shift.
Mentions: Figure 1 unambiguously demonstrates that for the SG/FM bilayers the HE ∼ T curve depends strongly on the composition of the SG layer. Previously, such sign-changeable behavior of HE against T was explained by the competition between long-range oscillatory RKKY couplings from the spins deep inside the SG layer and those close to the interface2122. In the present work, besides reconsidering the sign-changeable behavior, we focus on studying the HE and HC influenced by HFC. First we discuss the evolution of M-H hysteresis loops versus T. Figure 2 shows the M-H hysteresis loops obtained between 2 K and 20 K for the Ta(4 nm)/Fe11Au89(50 nm)/FeNi(5 nm)/Ta(2 nm) sample, after cooled from 300 K to 2 K under HFC = 50 kOe. The M-H hysteresis loop measured at 2 K clearly shows that a negative EB was established after field cooling. As shown in Fig. 2(a), when T increases from 2 K to 7 K, the ascending branch of the hysteresis loop shifts rightwards while the descending branch keeps almost unchanged. With further increasing in T from 8 K to 20 K, as displayed in Fig. 2(b), the hysteresis loop shrinks from both sides towards the center but the shift of ascending branch is more significantly than the descending branch. Therefore, the different T-dependent variation behaviors of the two loop branches lead to the concurrent peak on both the HE ∼ T and HC ∼ T curves, coinciding with the appearance of TP ∼ 7 K as shown in Fig. 1. These results indicate that the T-dependent magnetization reversal mechanisms and/or the thermodynamic spin relaxation at the descending and ascending branches may be quite different.

Bottom Line: Significantly, increasing in the magnitude of HFC reduces (increases) the value of HE in the negative (positive) region, resulting in the entire HE∼T curve to move leftwards and upwards.In the meanwhile, HFC variation has weak effects on HC.Thus this work reveals that the SG/FM bilayer system containing intimately coupled interface, instead of a single SG layer, is responsible for the novel EB properties.

View Article: PubMed Central - PubMed

Affiliation: National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P. R. China.

ABSTRACT
We report on the experimental and theoretical studies of cooling field (HFC) and temperature (T) dependent exchange bias (EB) in FexAu1-x/Fe19Ni81 spin glass (SG)/ferromagnet (FM) bilayers. When x varies from 8% to 14% in the FexAu1-x SG alloys, with increasing T, a sign-changeable exchange bias field (HE) together with a unimodal distribution of coercivity (HC) are observed. Significantly, increasing in the magnitude of HFC reduces (increases) the value of HE in the negative (positive) region, resulting in the entire HE∼T curve to move leftwards and upwards. In the meanwhile, HFC variation has weak effects on HC. By Monte Carlo simulation using a SG/FM vector model, we are able to reproduce such HE dependences on T and HFC for the SG/FM system. Thus this work reveals that the SG/FM bilayer system containing intimately coupled interface, instead of a single SG layer, is responsible for the novel EB properties.

No MeSH data available.


Related in: MedlinePlus