Systematic Control of Ferrimagnetic Skyrmions via Composition Modulation in Pt/Fe1-xTbx/Ta Multilayers

Magnetic skyrmions are topological spin textures that can be used as memory and logic components for advancing the next generation spintronics. In this regard, control of nanoscale skyrmions, including their sizes and densities, is of particular importance for enhancing the storage capacity of skyrmionic devices. Here, we propose a viable route for engineering ferrimagnetic skyrmions via tuning the magnetic properties of the involved ferrimagnets Fe_1-xTb_x. Via tuning the composition of Fe_1-xTb_x that alters the magnetic anisotropy and the saturation magnetization, the size of the ferrimagnetic skyrmion (d_s) and the average density (η_s) can be effectively tailored in [Pt/Fe_1-xTb_x/Ta]₁₀ multilayers. In particular, a stabilization of sub-50 nm skyrmions with a high density is demonstrated at room temperature. Our work provides an effective approach for designing ferrimagnetic skyrmions with the desired size and density, which could be useful for enabling high-density ferrimagnetic skyrmionics.

Neutron diffraction andab initiostudies on the fully compensated ferrimagnetic characteristics of Mn2V1-xCoxGa Heusler alloys

Neutron diffraction andab initiostudies were carried out on Mn₂V_1-xCo_xGa (x= 0, 0.25, 0.5, 0.75, 1) Heusler alloys which exhibits highT_Cfully compensated ferrimagnetic characteristics forx= 0.5. A combined analysis of neutron diffraction andab initiocalculations revealed the crystal structure and magnetic configuration which could not be determined from the x-ray diffraction and magnetic measurements. As reported earlier, Rietveld refinement of neutron diffraction data confirmedL2₁structure for Mn₂VGa andX_astructure for Mn₂CoGa. The alloys withx= 0.25 and 0.5 possessL2₁structure with Mn_(C)-Co disorder. As the Co concentration reaches 0.75, a structural transition has been observed from disorderedL2₁to disorderedX_a. Detailedab initiostudies also confirmed this structural transition. The reason for the magnetic moment compensation in Mn₂(V_1-xCo_x)Ga was identified to be different from that of the earlier reported fully compensated ferrimagnet (MnCo)VGa. With the help of neutron diffraction andab initiostudies, it is identified that the disorderedL2₁structure with antiparallel coupling between the ferromagnetically aligned magnetic moments of (Mn_(A)-Mn_(C)) and (V-Co) atom pairs enables the compensation in Mn₂V_1-xCo_xGa.

Compensated Ferrimagnetic Tetragonal Heusler Thin Films for Antiferromagnetic Spintronics

Fully compensated ferrimagnets with tetragonal crystal structure have the potential for large spin-polarization and strong out-of-plane magnetic anisotropy; hence, they are ideal candidates for high-density-memory applications. Tetragonal Heusler thin films with compensated magnetic state are realized by substitution of Pt in Mn_3-x Pt_x Ga. Furthermore, the bilayer formed from compensated/uncompensated Mn-Pt-Ga layers is utilized to accomplish exchange bias up to room temperature.