Antiferromagnetic MnNi tips for spin-polarized scanning probe microscopy

Forrester, Patrick; Bilgeri, Tobias; Patthey, F.; Brune, Harald; Natterer, Fabian Donat

doi:10.1063/1.5042530

Cited by 6 publications

(8 citation statements)

References 51 publications

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“…In this Rapid Communication, we demonstrate the zerofield stability of Ho/MgO using antiferromagnetic SP-STM tips that enable robust spin contrast in the absence of an external magnetic field [22]. At small magnetic fields we observe a significant number of state reversals that we trace back to the nuclear spin of Ho.…”

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confidence: 75%

“…We dose Ho atoms onto the sample at 10 K using a thoroughly degassed e-beam evaporator. We use antiferromagnetic Mn 88 Ni 12 tips [22]. Their out-of-plane spin polarization is tested by observing spin contrast on Ho atoms as they are switched by tunnel electrons above the threshold voltage V t = 73 mV [11,12,22].…”

mentioning

confidence: 99%

“…We use antiferromagnetic Mn 88 Ni 12 tips [22]. Their out-of-plane spin polarization is tested by observing spin contrast on Ho atoms as they are switched by tunnel electrons above the threshold voltage V t = 73 mV [11,12,22]. To adjust the magnetic field, the STM tip is retracted 5 nm for single retract/approach experiments and by 1 nm for multiple retractions/approaches.…”

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confidence: 99%

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Quantum state manipulation of single atom magnets using the hyperfine interaction

et al. 2019

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The magnetic quantum states of holmium single atom magnets on MgO(100) have proven extremely robust when exposed to high magnetic fields and temperatures up to 35 K. Here we address the stability of Ho at small magnetic fields, where the hyperfine interaction creates several avoided level crossings. Using spin-polarized scanning tunneling microscopy, we demonstrate quantum state control via Landau-Zener tunneling and stable magnetization at zero field. Our observations indicate a total spin ground state of J z = ±8. Combined quantum and classical control render Ho a promising qubit candidate.

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confidence: 75%

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confidence: 99%

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confidence: 99%

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Quantum state manipulation of single atom magnets using the hyperfine interaction

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“…4(b) shows that the two states have nearly the same occupation. This observation indicates that spin torque [54] and tip stray or exchange field effects [52,[55][56][57] are negligible at the tunneling conditions used and that magnetization reversal is mainly thermally induced. The magnetic ground state of the RE adatom is defined by m J4f , the magnetic quantum number related to J 4f resulting from the spin-orbit coupling of S 4f with the orbital moment L 4f .…”

Section: Rementioning

confidence: 88%

“…The spin polarization of the RE adatom's outer shell can be assessed by observing the magnetoresistance in spinpolarized STM measurements. To this purpose, we performed experiments using out-of-plane spin-polarized tips made of Mn 88 Ni 12 , which is an antiferromagnetic alloy [52]. Figure 3(a) displays a constant current STM image acquired on a sample with coexisting Ho and Dy adatoms on gr=Irð111Þ.…”

Section: Rementioning

confidence: 99%

Measuring the Intra-Atomic Exchange Energy in Rare-Earth Adatoms

et al. 2020

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We present the first experimental determination of the intra-atomic exchange energy between the inner 4f and the outer 6s5d shells in rare-earth elements. Inelastic electron tunneling spectroscopy on individual rare-earth atoms adsorbed on metal-supported graphene reveals an element-dependent excitation, with energy between 30 and 170 meV, linearly increasing with the spin angular momentum of the 4f shell. This observation is possible owing to the strong spin polarization of the outer shells, characteristic of rare-earth adatoms on graphene. This polarization gives rise to a giant magnetoresistance of up to 75% observed for Dy on graphene=Irð111Þ single-atom magnets. Density functional theory calculations of the 6s5d shell spin polarizations and of their intra-atomic exchange constants with the 4f shell yield exchange energies in agreement with the experimental values. These results prove that the description of the spin dynamics in RE considering only the 4f − 5d interaction is oversimplified. A more realistic treatment requires us to consider a multishell intra-atomic exchange in which both 6s and 5d shells are taken into account, with the 4f − 6s contribution possibly prevailing over the 4f − 5d one. Our findings are important for the general understanding of magnetism in rare earths, whether they are in bulk compounds or as surface adsorbed atoms and clusters. The results presented here also push for a revision of the description of the spin dynamics in rare-earth-based systems.

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Upgrade of a low-temperature scanning tunneling microscope for electron-spin resonance

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et al. 2019

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Electron spin resonance with a scanning tunneling microscope (ESR-STM) combines the high energy resolution of spin resonance spectroscopy with the atomic scale control and spatial resolution of STM. Here we describe the upgrade of a helium-3 STM with a 2D vector-field magnet (Bz = 8.0 T, Bx = 0.8 T) to an ESR-STM. The system is capable of delivering radio frequency (RF) power to the tunnel junction at frequencies up to 30 GHz. We demonstrate magnetic field-sweep ESR for the model system TiH/MgO/Ag(100) and find a magnetic moment of (1.004 ± 0.001) B. Our upgrade enables to toggle between a DC mode, where the STM is operated with the regular control electronics, and an ultrafast-pulsed mode that uses an arbitrary waveform generator for pump-probe spectroscopy or reading of spin-states. Both modes allow for simultaneous radiofrequency excitation, which we add via a resistive pick-off tee to the bias voltage path. The RF cabling from room temperature to the 350 mK stage has an average attenuation of 18 dB between 5 and 25 GHz. The cable segment between the 350 mK stage and the STM tip presently attenuates an additional 34+5−3 dB from 10 to 26 GHz and 38+3−2 dB between 20 and 30 GHz. We discuss our transmission losses and indicate ways to reduce this attenuation. We finally demonstrate how to synchronize the arrival times of RF and DC pulses coming from different paths to the STM junction, a prerequisite for future pulsed ESR experiments.

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Antiferromagnetic MnNi tips for spin-polarized scanning probe microscopy

Cited by 6 publications

References 51 publications

Quantum state manipulation of single atom magnets using the hyperfine interaction

Quantum state manipulation of single atom magnets using the hyperfine interaction

Measuring the Intra-Atomic Exchange Energy in Rare-Earth Adatoms

Upgrade of a low-temperature scanning tunneling microscope for electron-spin resonance

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