Interplay of electron correlations and localization in disordered <i>β</i>-tantalum films: Evidence from dc transport and spectroscopic ellipsometry study

Kovaleva, N. N.; Chvostová, D.; Bagdinov, A. V.; Petrova, M. G.; Демихов, Е. И.; Pudonin, F. A.; Dejneka, A.

doi:10.1063/1.4907862

Cited by 14 publications

(24 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The understanding of the found out-of-plane and in-plane magnetization properties, associated with self-organized ensembles of quasi-2D single-domain FM FeNi nanoislands, is quite important for the fundamental physics of magnetism, as well as for technological applications. [16]. During the deposition, the substrate temperature was 73 ± 3 ∘ C. The nominal film thickness (i.e., the thickness of the corresponding continuous film) was controlled by the deposition rate and time (see more details in [17]).…”

Section: Introductionmentioning

confidence: 99%

Out-of-Plane and In-Plane Magnetization Behavior of Dipolar Interacting FeNi Nanoislands around the Percolation Threshold

Stupakov

Bagdinov

Прохоров

et al. 2016

Journal of Nanomaterials

Self Cite

View full text Add to dashboard Cite

Magnetic properties of inhomogeneous nanoisland FeNi films were studied by SQUID magnetometry. The FeNi films with nominal thickness ranging from 0.6 to 2.0 nm were deposited by rf sputtering on Sitall glass substrates and covered by a protecting Al2O3 layer on the top. The SQUID data indicate pronounced irreversibility behavior for the out-of-plane temperature-dependent magnetization response (measured at H≃100 Oe) using zero-field cooling (ZFC) and field-cooled warming (FCW) after the applied dc magnetizing field Hm≃2 T for the FeNi samples with nominal thickness 1.1 nm ≲d≲1.8 nm, below the percolation threshold. The positive difference between the FCW and ZFC data identifies two irreversibility temperature scales, TB≈50 K and T⁎≈200 K, which can be associated with the superparamagnetic and superferromagnetic behavior in inhomogeneous nanoisland FeNi films, respectively. However, above the film percolation threshold, we observed a crossover from the out-of-plane to in-plane magnetization orientation. Here, the in-plane FCW-ZFC difference implies negative remanent magnetization response in the temperature range TB≲T≲T⁎. The observed magnetization properties can be associated with the presence of the superferromagnetic phase in self-assembled clusters of quasi-2D metallic magnetic FeNi nanoislands.

show abstract

Section: Introductionmentioning

confidence: 99%

Out-of-Plane and In-Plane Magnetization Behavior of Dipolar Interacting FeNi Nanoislands around the Percolation Threshold

Stupakov

Bagdinov

Прохоров

et al. 2016

Journal of Nanomaterials

Self Cite

View full text Add to dashboard Cite

show abstract

“…Let us follow the trends occurring in the Ta layer optical conductivity for the samples N2 50 , the 33-nm thick single Ta layer 30 , 31 , N5, and N6, which span a major part of the ( , ) Mooij plot related to the negative TCR values (see Fig. 5 ).…”

Section: Discussionmentioning

confidence: 99%

“…Recently, by using dc transport and wide-band spectroscopic ellipsometry experimental techniques we investigated disordered metallic -Ta films 30 , 31 , which are known to manifest negative TCR 32 . We discovered that with increasing degree of disorder the Drude contribution due to intraband absorption within the Ta 5d band at the Fermi level decreases and simultaneously the higher-energy optical bands appear as satellites at around 2–4 eV, where the associated optical SW is recovered.…”

Section: Introductionmentioning

confidence: 99%

“…In the giant magnetoresistance (GMR) layered nanostructures, the interlayer coupling between two ferromagnets is driven by the Ruderman-Kasuya-Kittel-Yoshida- (RKKY-) type 33 – 35 indirect exchange interactions via itinerant charge carriers of a nonmagnetic spacer. Having this in mind, here we propose to apply the elaborated approach 30 , 31 to study the dc transport and optical conductivity properties of the disordered metallic Ta interlayer in ultrathin multilayer structures Ta– similar to those exhibiting the GMR effect. We investigated the rf-sputtered multilayer films (MLFs) (Ta–FeNi) in two limits of the FeNi layer thickness (i) when it is discontinuous and consists of inhomogeneously distributed single-domain ferromagnetic nanoislands having lateral sizes of 5–30 nm 36 and possessing giant magnetic moments of 10 –10 (where is the Bohr magneton) and (ii) when its nominal thickness is varied across the FeNi film percolation threshold around 1.5–1.8 nm 37 , 38 (see the schematic picture of the MLF structure (Ta–FeNi) involving the nanoisland FeNi layer in Fig.…”

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Control of Mooij correlations at the nanoscale in the disordered metallic Ta–nanoisland FeNi multilayers

Kovaleva

Kusmartsev

Mekhiya

et al. 2020

Sci Rep

Self Cite

View full text Add to dashboard Cite

Localisation phenomena in highly disordered metals close to the extreme conditions determined by the Mott-Ioffe-Regel (MIR) limit when the electron mean free path is approximately equal to the interatomic distance is a challenging problem. Here, to shed light on these localisation phenomena, we studied the dc transport and optical conductivity properties of nanoscaled multilayered films composed of disordered metallic Ta and magnetic FeNi nanoisland layers, where ferromagnetic FeNi nanoislands have giant magnetic moments of 10$$^3$$ 3 –10$$^5$$ 5 Bohr magnetons ($$\mu _{\mathrm{B}}$$ μ B ). In these multilayered structures, FeNi nanoisland giant magnetic moments are interacting due to the indirect exchange forces acting via the Ta electron subsystem. We discovered that the localisation phenomena in the disordered Ta layer lead to a decrease in the Drude contribution of free charge carriers and the appearance of the low-energy electronic excitations in the 1–2 eV spectral range characteristic of electronic correlations, which may accompany the formation of electronic inhomogeneities. From the consistent results of the dc transport and optical studies we found that with an increase in the FeNi layer thickness across the percolation threshold evolution from the superferromagnetic to ferromagnetic behaviour within the FeNi layer leads to the delocalisation of Ta electrons from the associated localised electronic states. On the contrary, we discovered that when the FeNi layer is discontinuous and represented by randomly distributed superparamagnetic FeNi nanoislands, the Ta layer normalized dc conductivity falls down below the MIR limit by about 60%. The discovered effect leading to the dc conductivity fall below the MIR limit can be associated with non-ergodicity and purely quantum (many-body) localisation phenomena, which need to be challenged further.

show abstract

Collective magnetic response of inhomogeneous nanoisland FeNi films around the percolation transition

et al. 2018

View full text Add to dashboard Cite

By using superconducting quantum interference device (SQUID) magnetometry we investigated anisotropic high-field (H 7 T) low-temperature (10 K) magnetization response of inhomogeneous nanoisland FeNi films grown by rf sputtering deposition on Sitall (TiO2) glass substrates. In the grown FeNi films, the FeNi layer nominal thickness varied from 0.6 to 2.5 nm, across the percolation transition at the dc ≃ 1.8 nm. We discovered that, beyond conventional spin-magnetism of Fe21Ni79 permalloy, the extracted out-of-plane magnetization response of the nanoisland FeNi films is not saturated in the range of investigated magnetic fields and exhibits paramagnetic-like behavior. We found that the anomalous out-of-plane magnetization response exhibits an escalating slope with increase in the nominal film thickness from 0.6 to 1.1 nm, however, it decreases with further increase in the film thickness, and then practically vanishes on approaching the FeNi film percolation threshold. At the same time, the in-plane response demonstrates saturation behavior above 1.5-2 T, competing with anomalously large diamagnetic-like response, which becomes pronounced at high magnetic fields. It is possible that the supported-metal interaction leads to the creation of a thin charge-transfer (CT) layer and a Schottky barrier at the FeNi film/Sitall (TiO2) interface. Then, in the system with nanoscale circular domains, the observed anomalous paramagnetic-like magnetization response can be associated with a large orbital moment of the localized electrons. In addition, the inhomogeneous nanoisland FeNi films can possess spontaneous ordering of toroidal moments, which can be either of orbital or spin origin. The system with toroidal inhomogeneity can lead to anomalously strong diamagnetic-like response. The observed magnetization response is determined by the interplay between the paramagnetic-and diamagnetic-like contributions.

show abstract

Interplay of electron correlations and localization in disordered β-tantalum films: Evidence from dc transport and spectroscopic ellipsometry study

Cited by 14 publications

References 10 publications

Out-of-Plane and In-Plane Magnetization Behavior of Dipolar Interacting FeNi Nanoislands around the Percolation Threshold

Out-of-Plane and In-Plane Magnetization Behavior of Dipolar Interacting FeNi Nanoislands around the Percolation Threshold

Control of Mooij correlations at the nanoscale in the disordered metallic Ta–nanoisland FeNi multilayers

Collective magnetic response of inhomogeneous nanoisland FeNi films around the percolation transition

Contact Info

Product

Resources

About