Abstract

A new method for the determination of anisotropy field strength in specimens with uniaxial anisotropy is described. Longitudinal MOKE is used in combination with a rotating magnetic field. Due to sufficient large field strength, a Stoner–Wohlfarth-like magnetisation reversal process can be realised. By correcting higher-order MOKE terms, a highly accurate calculation of H_k is demonstrated on different Fe, NiFe and Co ultra thin films.

Author Keywords: Magneto-optical measurements; Anisotropy – uniaxial; Torque measurements; Second-order magneto-optical effect; Quadratic magneto-optical effect; QMOKE; Voigt effect; Ultrathin film

Article Outline

1. Introduction

2. Sample preparation

3. Experimental MOKE set-up

4. Experimental results and discussion

4.1. Longitudinal Kerr loops and sample orientation

4.2. Procedure for ROTMOKE: separation of QMOKE contributions due to the Voigt effect

4.3. Determination of the anisotropy field strength

4.4. Experimental results

4.4.1. Ta/4 nm Py/Ta sandwich with field-induced uniaxial anisotropy of the permalloy

4.4.2. Ta/Cu/Fe/Cu/Ta system

4.4.3. Ta/Cu/Co/Cu/Ta system

5. Discussion

6. Conclusion

Acknowledgements

References

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Fig. 1. Longitudinal Kerr loops of a 4 nm Fe specimen with a transversal applied field and different orientations of the hard axis (ha) with respect to the sensitivity direction of the MOKE set-up (X-axis).

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Fig. 2. (a) Hard axis (ha) and easy axis (ea) Kerr loop of a 4 nm Fe layer and (b) anhysteretic Kerr loops in ha and ea directions (details see text).

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Fig. 3. Schematical picture of the directions of applied field H() and normalised magnetisation m(), respectively. The components m_l and m_t of m for both symmetric states with respect to the X-axis are indicated in (a) for quadrant 1 and 4, and in (b) for quadrant 1 and 3.

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Fig. 4. Normalised Kerr rotation in hard axis (ha) and easy axis (ea) direction for a 4 nm Py film sandwiched between Ta.

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Fig. 5. Normalised longitudinal magnetisation component m_l as a function of angle of the applied field, H=10 Oe, 4 nm Py.

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Fig. 6. Calculated normalised torque moment l() as a function of angle of the applied field, H=10 Oe, 4  nm Py.

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Fig. 7. Normalised longitudinal magnetisation component m_l as a function of angle of the applied field, H=40 Oe, 4 nm Py.

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Fig. 8. Calculated normalised torque moment l() as a function of angle of the applied field, H=40 Oe, 4 nm Py.

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Fig. 9. Normalised longitudinal magnetisation component m_l as a function of angle of the applied field, H=20 Oe, 4 nm Fe.

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Fig. 10. Calculated normalised torque moment l() as a function of angle of the applied field H=20 Oe, 4 nm Fe.

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Fig. 11. The dependence of calculated H_k versus the applied field strength for ea and ha oriented parallel to the longitudinal direction of ROTMOKE experiment, specimen 4 nm Fe.

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Fig. 12. The amplitude of the corrected Kerr rotation for ea and ha parallel to the longitudinal direction of ROTMOKE experiment, specimen 4 nm Fe.

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Fig. 13. Normalised longitudinal magnetisation component m_l as a function of angle of the applied field, H=20 Oe, 0.8 nm Co film.

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Fig. 14. Calculated normalised torque moment l() as a function of angle of the applied field, H=20 Oe, 0.8 nm Co film.

References

1. Q.-M. Zhong, A.S. Arrott, B. Heinrich and Z. Celinski. J. Appl. Phys. 67 (1990), p. 4448. Abstract-INSPEC   | $Order Document | Full Text via CrossRef

2. Q.-M. Zhong, A.S. Arrott, B. Heinrich and Z. Celinski. J. Magn. Magn. Mater. 104–107 (1992), p. 1837. Abstract | Abstract + References | PDF (325 K)

3. R.M. Osgood III, R.L. White and B.M. Clemens. IEEE Trans. Magn. 31 (1995), p. 3331.

4. R. Mattheis and G. Quednau. Phys. Stat. Sol. (a) 172₂ (1999), p. R7. Abstract-Compendex | Abstract-INSPEC   | $Order Document

5. R.M. Osgood III, S.D. Bader, B.M. Clemens, R.L. White and H. Matsuyama. J. Magn. Magn. Mater. 182 (1998), p. 297. SummaryPlus | Full Text + Links | PDF (510 K)

6. K. Postava, H. Jaffres, A. Schuhl, F. Nguyen Van Dau, M. Goiran and A.R. Fert. J. Magn. Magn. Mater. 172 (1997), p. 199. SummaryPlus | Full Text + Links | PDF (709 K)

7. A. Hubert and R. Schäfer, Magnetic Domains. Springer, Berlin (1998).

8. H. Hornauer, T.M. Atmono and K. Röll. J. Magn. Magn. Mater. 83 (1990), p. 551. Abstract | Abstract + References | PDF (154 K)

9. F.B. Humphrey and A.R. Johnston. Rev. Sci. Instrum. 34 (1963), p. 348. Full Text via CrossRef

10. C.S. Gudeman. IEEE Trans. Magn. 26 5 (1990), p. 2580. Abstract-Compendex | Abstract-INSPEC   | $Order Document | Full Text via CrossRef

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