Mechanically exfoliated two-dimensional ferromagnetic materials (2D FMs) possess long-range ferromagnetic order and topologically nontrivial skyrmions in few layers. However, because of the dimensionality effect, such few-layer systems usually exhibit much lower Curie temperature (T _C) compared to their bulk counterparts. It is therefore of great interest to explore effective approaches to enhance their T _C, particularly in wafer-scale for practical applications. Here, we report an interfacial proximity-induced high-T _C 2D FM Fe₃GeTe₂ (FGT) via A-type antiferromagnetic material CrSb (CS) which strongly couples to FGT. A superlattice structure of (FGT/CS)_n, where n stands for the period of FGT/CS heterostructure, has been successfully produced with sharp interfaces by molecular-beam epitaxy on 2-inch wafers. By performing elemental specific X-ray magnetic circular dichroism (XMCD) measurements, we have unequivocally discovered that T _C of 4-layer Fe₃GeTe₂ can be significantly enhanced from 140 K to 230 K because of the interfacial ferromagnetic coupling. Meanwhile, an inverse proximity effect occurs in the FGT/CS interface, driving the interfacial antiferromagnetic CrSb into a ferrimagnetic state as evidenced by double-switching behavior in hysteresis loops and the XMCD spectra. Density functional theory calculations show that the Fe-Te/Cr-Sb interface is strongly FM coupled and doping of the spin-polarized electrons by the interfacial Cr layer gives rise to the T _C enhancement of the Fe₃GeTe₂ films, in accordance with our XMCD measurements. Strikingly, by introducing rich Fe in a 4-layer FGT/CS superlattice, T _C can be further enhanced to near room temperature. Our results provide a feasible approach for enhancing the magnetic order of few-layer 2D FMs in wafer-scale and render opportunities for realizing realistic ultra-thin spintronic devices.

Purpose

Prognostic markers that identify patients with stage II colon cancers who are at the risk of recurrence are essential to personalize therapy. We evaluated the potential of GIV/Girdin as a predictor of recurrence risk in such patients.

Experimental design

Expression of full-length GIV was evaluated by IHC using a newly developed mAb together with a mismatch repair (MMR)-specific antibody panel in three stage II colon cancer patient cohorts, that is, a training (n = 192), test (n = 317), and validation (n = 181) cohort, with clinical follow-up data. Recurrence risk stratification models were established in the training cohort of T3, proficient MMR (pMMR) patients without chemotherapy and subsequently validated.

Results

For T3 pMMR tumors, GIV expression and the presence of lymphovascular invasion (LVI) were the only factors predicting recurrence in both training (GIV: HR, 2.78, P = 0.013; LVI: HR, 2.54, P = 0.025) and combined test and validation (pooled) cohorts (GIV: HR, 1.85, P = 0.019; LVI: HR, 2.52, P = 0.0004). A risk model based on GIV expression and LVI status classified patients into high- or low-risk groups; 3-year recurrence-free survival was significantly lower in the high-risk versus low-risk group across all cohorts [Training: 52.3% vs. 84.8%; HR, 3.74, 95% confidence interval (CI), 1.50-9.32; Test: 85.9% vs. 97.9%, HR, 7.83, 95% CI, 1.03-59.54; validation: 59.4% vs. 84.4%, HR, 3.71, 95% CI, 1.24-11.12].

Conclusions

GIV expression status predicts recurrence risk in patients with T3 pMMR stage II colon cancer. A risk model combining GIV expression and LVI status information further enhances prediction of recurrence. Further validation studies are warranted before GIV status can be routinely included in patient management algorithms. Clin Cancer Res; 22(14); 3488-98. ©2016 AACR.