Magnetic reversal in rare-earth free Mn4 − xNixN epitaxial films below and above Ni composition needed for magnetic compensation around room temperature

Abstract

Ferrimagnets close to the magnetic compensation are excellent candidates to spin-torque-based spintronic applications, as their small magnetizations allow lowering switching currents. Here, we studied the magnetic compensation of Mn4 − xNixN epitaxial films by performing x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements at the L2,3 absorption edges of Mn and Ni atoms and compared them with those of Ni3FeN films. The XAS spectrum of the Ni3FeN films exhibits shoulders at approximately 2 eV above the Ni L2,3 main peaks, originating from orbitals hybridization between Ni 3d at face-centered (II) sites and N 2p at body-centered sites. However, such shoulders are not observed at the Ni L2,3 edges of the Mn4 − xNixN films (x = 0.1 and 0.25). These results indicate that the orbitals of Ni atoms do not hybridize with those of N atoms. Hence, Ni atoms preferentially occupy corner (I) sites, where hybridization is weak because of the relatively long distance between Ni at I sites and N atoms. The XMCD signals of Mn and Ni atoms reverse sign between x = 0.1 and 0.25. This shows that the directions of the magnetic moments carried by Mn and Ni atoms are reversed, indicating that the magnetic compensation occurs in the range 0.1 < x < 0.25. In addition, the signs of Mn(I) XMCD signals are opposite to those of Mn(II) and Ni for each composition. Thus, the magnetic moments of Ni atoms are aligned parallel to those of Mn(II) regardless of whether x is below or above the compensation point.

Current-driven domain wall dynamics in ferrimagnetic Ni-doped Mn4N films : very large domain wall velocities and reversal of motion direction across the magnetic compensation point

“…2b indicates net magnetization parallel/anti-parallel to the Mn(I) magnetic moment. In agreement with previous results 36,37 , M s is observed to decrease with increasing Ni content and to change direction for x between 0.15 and 0.2. Note that for the nominal Ni content x = 0.15, a difference in the net magnetization direction is observed between the 10 nm and 30 nm thick films.…”

“…In this paper, we focus on Ni-doped Mn 4 N thin films epitaxially grown on STO(001) substrates 36 . 10 nm and 30 nm thick Mn 4−x Ni x N films, with nominal x varying between 0.1 and 0.25, were grown by molecular beam epitaxy on STO(001) substrates and capped with a 3 nm thick SiO 2 layer.…”

“…Our previous X-ray magnetic circular dichroism (XMCD) measurements 36 showed that Ni occupies preferentially the Mn(I) sites of Mn 4 N. Since the moment carried by Ni atoms is anti-parallel to that of Mn(I), increasing the Ni atomic content allows reducing the overall magnetization. Beyond a critical Ni content, the net magnetization direction is thus expected to reverse with respect to the original one, i.e.…”

Current-Driven Domain Wall Dynamics in Ferrimagnetic Nickel-Doped Mn4N Films: Very Large Domain Wall Velocities and Reversal of Motion Direction across the Magnetic Compensation Point

“…35 In this paper, we focus on Ni-doped Mn 4 N thin films epitaxially grown on STO(001) substrates. 36 The 10 and 30 nm thick Mn 4−x Ni x N films, with nominal x varying between 0.1 and 0.25, were grown by molecular beam epitaxy on STO(001) substrates and capped with a 3 nm thick SiO 2 layer. Scanning transmission electron microscopy (STEM), reflection highenergy electron diffraction and X-ray diffraction measurements were performed to check their crystalline quality.…”

Spin‐Torque Switching in Rare‐Earth‐Free Compensated Ferrimagnet Mn4N Films

“…The Curie temperature is around 730 K. [17,18] Moreover, the magnetic properties of the Mn 4 N can be modulated through chemical doping, such as a Ni-doping could produce a complete magnetization compensation ( M net = 0). [19,20] In the present report, we will explore the spin-orbitronic physics in the single crystalline C-FIM Mn 4 N films. In particular, the current-induced spin-orbit torque (SOT) arising from the spin Hall effect of the adjacent heavy metal Pt layer is utilized to switch the perpendicular magnetizations of the Mn 4 N films with a thickness up to 60 nm.…”