کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8153410 | 1524765 | 2018 | 27 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
High-field magnetoconductance in La-Sr manganites of FM and AFM ground states
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
فیزیک و نجوم
فیزیک ماده چگال
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
Large-grain La1-xSrxMnO3 ceramic samples of compositions xâ¯=â¯0.45 and 0.55, representing the ferromagnetic (FM) and A-type antiferromagnetic (AFM) ground states, were produced via classical sintering at 1500â¯Â°C of cold-pressed sol-gel prepared single-phase nanoparticles. Using the same precursors, nanogranular forms of both manganite ceramics were prepared by fast spark plasma sintering at low temperature of 900â¯Â°C, which limits the growth of crystal grains. The magnetotransport of both the bulk and nanogranular forms was investigated in a broad range of magnetic fields up to 130â¯kOe and analyzed on the basis of detailed magnetic measurements. Both the large-grain and nanogranular systems with xâ¯=â¯0.45, possessing a pure FM state with similar Curie tempereature TCâ¯ââ¯345â¯K), show nearly the same conductivity enhancement in external fields when expressed relatively to the zero-field values. This positive magnetoconductance (MC) can be separated into two terms: (i) the hysteretic low-field MC that reflects the field-induced orientation of magnetic moments of individual grains, and (ii) the high-field MC that depends linearly on external field. In the case of large-grain ceramics with xâ¯=â¯0.55, a partially ordered FM state formed below TCâ¯=â¯264â¯K is replaced by pure A-type AFM ground state below 204â¯K. This A-type AFM state is characterized by positive magnetoconductance that is essentially of quadratic dependence on external field in the investigated range up to 130â¯kOe. On contrary, the nanogranular product with xâ¯=â¯0.55 exhibits a mixed FM/AFM state at low temperatures, and, as a consequence, its magnetotransport combines the features of FM and A-type AFM systems, in which the quadratic term is much enhanced and clearly dominates at high fields. For interpretation of observed behaviors, the theory of grain-boundary tunneling is revisited.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Magnetism and Magnetic Materials - Volume 456, 15 June 2018, Pages 167-178
Journal: Journal of Magnetism and Magnetic Materials - Volume 456, 15 June 2018, Pages 167-178
نویسندگان
ZdenÄk Jirák, OndÅej Kaman, Karel KnÞek, Petr Levinský, Martin MÃÅ¡ek, Pavel Veverka, JiÅà Hejtmánek,