誘導(dǎo)的反鐵磁→鐵磁一級(jí)磁相變
(中南大學(xué) 應(yīng)用物理與熱能工程系，長(zhǎng)沙 410083)
摘 要: 在脈沖強(qiáng)磁場(chǎng)中測(cè)量了Gd1-xLaxMn2Ge2(x=0.06，0.07)化合物在不同溫度下的磁化曲線。結(jié)果表明，當(dāng)這些化合物處于反鐵磁狀態(tài)的溫度范圍內(nèi)時(shí)，Mn次晶格中發(fā)生了場(chǎng)誘導(dǎo)的從反鐵磁狀態(tài)到鐵磁狀態(tài)的一級(jí)磁相變。隨著溫度的降低，相變臨界磁場(chǎng)逐漸增大，達(dá)到最大值后，隨著溫度的進(jìn)一步降低，臨界磁場(chǎng)很快減小；隨La含量的增加，相變臨界磁場(chǎng)也很快減小。在交換相互作用的分子場(chǎng)模型基礎(chǔ)上， 考慮層面間Mn-Mn交換作用隨晶格常數(shù)a以及溫度的變化，從理論上計(jì)算了這種場(chǎng)誘導(dǎo)的反鐵磁→鐵磁一級(jí)磁相變所對(duì)應(yīng)的臨界磁場(chǎng)，理論計(jì)算結(jié)果較好 地 描述了臨界磁場(chǎng)隨溫度的變化規(guī)律。理論模型也較好地解釋了在這些化合物中發(fā)生的從亞鐵磁結(jié)構(gòu)到反鐵磁結(jié)構(gòu)再到鐵磁結(jié)構(gòu)的一級(jí)自發(fā)磁相變。
關(guān)鍵字: 稀土金屬間化合物；交換相互作用；磁相變
antiferromagnetism→ferromagnetism
transitions in Gd1-xLaxMn2Ge2
(x=0.06，0.07) intermet
（Department of Applied Physics and Heat Energy Engineering，
Central South University，Changsha 410083，China）
Abstract:The magnetization curves of Gd1-xLaxMn2Ge2(x=006, 0.07)intermetallic compounds were measured in the pulse magnetic field at different temperatures. The results show that the field-induced antiferromagnetism→ferromagnetism transitions in Mn-sublattice are founded in the antiferromagnetic state temperature range. The critical transition field tends to increase with decreasing the temperature，after reaching the maximum，the critical field decreases significantly. With the in crease of the content of La，the critical transition fields also decrease significantly. In the approximation of molecular field of exchange interaction， the critical transition fields are calculated by taking into account of lattice parameter a and temperature dependence of the interlayer Mn-Mn exchange parameter. The theoretical results well describe the temperature dependence of critical transition field. Theory also well explain the spontaneous first order ferrimagnetism→antiferromagnetism→ferrom agnetism transition in the studied compounds.
Key words: rare earth intermetallic compound; exchange in teraction; magnetic phase transition
