Temperature and cooling field dependent exchange coupling in [Cr/Gd]₅ multilayers

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• 作者：Z. W. Jiao ; H. J. Chen ; W. D. Jiang ; J. F. Wang ; S. J. Yu ; Y. L. Hou ; B. Lu and Q. L. Ye
• 刊名：physica status solidi (a)
• 出版年：2016
• 出版时间：September 2016
• 年：2016
• 卷：213
• 期：9
• 页码：2531-2536
• 全文大小：736K
• ISSN：1862-6319

文摘

Exchange coupling has been investigated in the [Cr/Gd]lass="math-equation-construct">lass="math-equation-image">l="true" class="math-equation-mathml" style="display:none">l:math xmlns:mml="http://www.w3.org/1998/Math/MathML">lns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">w>w>5l:math> multilayers deposited at 25, 200, and lass="math-equation-construct">lass="math-equation-image">l="true" class="math-equation-mathml" style="display:none">l:math xmlns:mml="http://www.w3.org/1998/Math/MathML">lns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">400w>width="thinmathspace">∘w>l:math>C, where the Néel temperature (lass="math-equation-construct">lass="math-equation-image">l="true" class="math-equation-mathml" style="display:none">l:math xmlns:mml="http://www.w3.org/1998/Math/MathML">lns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">lic">Tl">Nl:math>) of antiferromagnetic Cr is slightly higher than the Curie temperature (lass="math-equation-construct">lass="math-equation-image">l="true" class="math-equation-mathml" style="display:none">l:math xmlns:mml="http://www.w3.org/1998/Math/MathML">lns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">lic">Tl">Cl:math>) of ferromagnetic Gd. It was found that the exchange coupling existed not only at lass="math-equation-construct">lass="math-equation-image">l="true" class="math-equation-mathml" style="display:none">l:math xmlns:mml="http://www.w3.org/1998/Math/MathML">lns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">lic">Tl">Clns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML"><lns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML" mathvariant="italic">Tlns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML"><lns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">lic">Tl">Nl:math>, but also above the temperature (lass="math-equation-construct">lass="math-equation-image">l="true" class="math-equation-mathml" style="display:none">l:math xmlns:mml="http://www.w3.org/1998/Math/MathML">lns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">lic">Tl">Nl:math>) of antiferromagnetic orderings with incommensurate spin-density wave structures transiting to paramagnetic state. These results can be discussed in terms of the crucial role played by the antiferromagnetic spins of Cr with commensurate spin-density wave structures in the vicinity of the Cr/Gd interfaces. Moreover, the exchange coupling of the multilayers grown at different temperatures exhibited different dependencies on the measuring temperature and the cooling field, respectively. Positive exchange bias was observed in the multilayers grown at 200 and lass="math-equation-construct">lass="math-equation-image">l="true" class="math-equation-mathml" style="display:none">l:math xmlns:mml="http://www.w3.org/1998/Math/MathML">lns:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">400w>width="thinmathspace">∘w>l:math>C. The interfacial roughness, grain size, and the antiferromagnetic orderings of Cr may be responsible for the anomalous exchange coupling of the multilayers. In addition, the competition between the exchange coupling at Cr/Gd interfaces and the external field-Cr surface magnetic coupling can explain the appearance of negative or positive exchange bias.