層狀鹵化物雙鈣鈦礦半金屬—可在室溫下出現(xiàn)？

半金屬鐵磁體（HMF）在一個自旋通道中存在電子的金屬性，而同時(shí)在另一個自旋通道中又存在絕緣性，可產(chǎn)生完全的自旋極化電流，并且被認(rèn)為是從磁性存儲器到自旋極化的許多自旋電子學(xué)應(yīng)用的關(guān)鍵候選者隧道設(shè)備。為了開發(fā)高性能的自旋電子器件，HMF高度需要三個標(biāo)準(zhǔn)：1）高的室溫（RT）應(yīng)用的居里溫度（Tc）；2）寬的半金屬間隙（ΔHM）從而有效地防止熱激發(fā)引起的載流子自旋翻轉(zhuǎn)轉(zhuǎn)變，以及3）大塊體磁晶各向異性能（MAE）可克服由熱波動引起的自旋隨機(jī)且不可控的切換。盡管人們已從理論和實(shí)驗(yàn)角度報(bào)道了一些HMF，但它們大多數(shù)還不能同時(shí)滿足所有這些標(biāo)準(zhǔn)。

該研究確定了一種層狀鹵化雙鈣鈦礦材料（HMFs），Cs4FePb2Cl12，具有高Tc、寬ΔHM和大MAE的半金屬基態(tài)。清華大學(xué)材料科學(xué)與工程學(xué)院先進(jìn)材料（MOE）重點(diǎn)實(shí)驗(yàn)室的劉劍波教授和北京計(jì)算科學(xué)研究中心的黃兵研究員共同領(lǐng)導(dǎo)的團(tuán)隊(duì)，使用基于第一性原理計(jì)算方法，在大量LHDPs中篩選了具有標(biāo)準(zhǔn)化學(xué)組成的Cs4MB2X12材料。有趣的是，在幾種具有良好動態(tài)和熱穩(wěn)定性的化合物中，他們確定Cs4FePb2Cl12可表現(xiàn)出半金屬基態(tài)，其計(jì)算的Tc高于RT（Tc ~450 K）。同時(shí)，Cs4FePb2Cl12的ΔHM~0.55 eV較寬、MAE~380μeV/ Fe較大，使Cs4FePb2Cl12成為自旋電子學(xué)中最好的半金屬材料之一。值得注意的是，當(dāng)Cs4FePb2Cl12層的厚度減小到單層時(shí)，它仍可以以高Tc~370 K和強(qiáng)MAE~318 μeV / Fe維持半金屬性。Cs4FePb2Cl12的磁耦合和MAE均可用施加外部應(yīng)變加以有效地操縱。Cs4FePb2Cl12單層的發(fā)現(xiàn)，豐富了2D磁體家族，也有望應(yīng)用于從傳感到數(shù)據(jù)存儲的廣泛領(lǐng)域。 該文近期發(fā)表于npj Computational Materials5: 114(2019)，英文標(biāo)題與摘要如下，點(diǎn)擊左下角“閱讀原文”可以自由獲取論文PDF。

Prediction ofroom-temperature half-metallicity in layered halide double perovskites Jian Xu,Changsong Xu,Jian-Bo Liu,LaurentBellaiche,Hongjun Xiang,Bai-Xin Liu &Bing Huang Half-metallic ferromagnets (HMFs) that possess intriguing physical properties with completely spin-polarized current are key candidates for high-efficiency spintronic devices. However, HMFs that could simultaneously have high Curie temperature (Tc), wide half-metallic gap (ΔHM), and large bulk magnetocrystalline anisotropy energy (MAE) are very rare, which significantly restrict their room-temperature (RT) applications. In this article, through materials screening in layered halide double perovskites (LHDPs), we have theoretically identified that Cs4FePb2Cl12, which has good crystallographic, dynamic and thermal stabilities, possesses an intrinsichalf-metallic ground-state with a highTc~450K. Interestingly, the long-range ferromagnetic ordering in bulk Cs4FePb2Cl12is contributed by the strong super-superexchange interactions between the neighboring Fedorbitals mediated by different anionic Clporbitals. The highTcoflayered Cs4FePb2Cl12can be well maintained even in the monolayer limitation, i.e.,Tc~370K for Cs4FePb2Cl12monolayer, which is critical for nanoscale device applications. Moreover, both bulk and monolayer Cs4FePb2Cl12can exhibit wide ΔHM~0.55eV and large MAE >320μeV/Fe, comparable to that of the best HMFs reported in the literature. Our findings can significantly extend the potentials of LHDPs for high-temperature spintronic applications.