Study of the negative magneto-resistance of single proton-implanted lithium-doped ZnO microwires

Lorite, I.; Zandalazini, C.; Esquinazi, P.; Spemann, D.; Friedländer, Stefan; Pöppl, Álan Gomes; Michalsky, Tom; Grundmann, Marius; Vogt, J.; Meijer, Jan; Heluani, S. P.; Ohldag, Hendrik; Adeagbo, Waheed A.; Nayak, Sanjeev K.; Hergert, W.; Ernst, A.; Hoffmann, Martin

doi:10.1088/0953-8984/27/25/256002

Cited by 10 publications

(19 citation statements)

References 30 publications

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“…All Li-doped ZnO microwires are highly insulating with a resistance larger than 10 10 Ω at room temperature [14]. At the energy used for implantation of H + in our samples, a significant concentration of protons as well as defects (Zn-and O-vacancies) are localized only within a ∼ 10 nm surface region according to SRIM simulations [20] (see also Fig.…”

Section: Methodsmentioning

confidence: 97%

“…For comparison, a second ZnO wire without Li doping but with a similar proton implantation dose as the first one, has also been measured. This latter wire does not show any magnetic order at room temperature [14]. Both microwires are characterized by 1/f -like noise.…”

Section: Introductionmentioning

confidence: 88%

“…In fact, it was experimentally verified that most of the magnetic signal comes from the near surface region [18]. The temperature dependence of the resistance can be understood using a simple parallel resistor model that takes into account two contributions to the total conduction, one from the near surface region and the other from a non-magnetic region further inside the wire, where a lower H + doping also reduces, but in a minor grade, the resistance [14]. Transport studies of H + -implanted ZnO single crystals [21] and microwires [22] indicate that the metallic-like contribution is associated with the hydrogen-rich near surface region of the samples.…”

Section: Methodsmentioning

confidence: 99%

“…Transport studies of H + -implanted ZnO single crystals [21] and microwires [22] indicate that the metallic-like contribution is associated with the hydrogen-rich near surface region of the samples. The photoluminescence spectra at 300 K and the magnetic properties (SQUID, XMCD and magnetoresistance) of the wires have been reported recently [10,14].…”

Section: Methodsmentioning

confidence: 99%

“…By implantation of protons at energy 300 eV one can obtain a magnetically ordered 10 nm thick surface regions in ZnO:Li microwires. These regions show clear ferromagnetic characteristics, as revealed by SQUID magnetometry and x-ray magnetic circular dichroism (XMCD) [10] as well as a negative magnetoresistance [14]. Therefore, increase of the noise associated with decrease of the effective size of the magnetically ordered sample volume may become a limiting factor for the applications of magnetic oxide nanowires in spintronics.…”

Section: Introductionmentioning

confidence: 99%

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Conductivity fluctuations in proton-implanted ZnO microwires

et al. 2016

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Abstract. The electric noise can be an important limitation for applications of conducting elements of size in the nanometer range. The intrinsic electrical noise of prospective materials for opto-spintronics applications like ZnO has not been characterized yet. In this study we have investigated the conductivity fluctuations in 10 nm thick current paths produced by proton implantation of ZnO microwires at room temperature. The voltage noise under a constant dc current bias in undoped as well as in Li-doped microwires is characterized by 1/f a power spectra with a ∼ 1. The noise intensity scales with the square of the bias current pointing out to biasindependent resistivity fluctuations as a source of the observed noise. The normalized power spectral density appears inversely proportional to the number of carriers in the probed sample volume, in agreement with the phenomenological Hooge law. For the proton-implanted ZnO microwire and at 1 Hz we obtain a normalized power spectral density as low as ∼ 10 −11 Hz −1 . Conductivity fluctuations in proton-implanted ZnO microwires2

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Section: Methodsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 88%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Conductivity fluctuations in proton-implanted ZnO microwires

et al. 2016

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Defect‐Induced Magnetism in Nonmagnetic Oxides: Basic Principles, Experimental Evidence, and Possible Devices with ZnO and TiO₂

Esquinazi

Hergert

Stiller

et al. 2020

Physica Status Solidi (b)

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The magnetic moment and the magnetic order induced by localized defects, like vacancies, interstitials, and/or nonmagnetic (NM) ions, in a NM oxide atomic lattice are discussed. When the defect concentration is of the order of or larger than ≈3 at%, magnetic order at room temperature can appear. Herein, the theoretical basic principles needed to understand and compute this new magnetic phenomenon in solids are developed in detail. In particular, the main results of density functional theory (DFT) calculations are used to estimate the magnetization and X‐ray magnetic circular dichroism (XMCD) values. The main experimental evidences on this phenomenon are reviewed, especially magnetization, the element‐specific XMCD, and transport properties in two selected oxides, ZnO and TiO2. Emphasis is given on the simplicity and efficiency ion irradiation methods have to trigger magnetic order in these oxides as well as a very sensitive method to characterize magnetic impurities. Two possible applications of this phenomenon are discussed, namely spin filtering at magnetic/NM interfaces in ZnO and perpendicular magnetic anisotropy triggered in TiO2 anatase microstructures. The existing literature on defect‐induced magnetism in oxides is shortly reviewed, which provides further evidence on the robustness of this phenomenon in solids.

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Magnetic and Electronic Properties of Complex Oxides from First‐Principles

Hoffmann

Ernst

Hergert

et al. 2020

Physica Status Solidi (b)

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The theoretical treatment of complex oxide structures requires a combination of efficient methods to calculate structural, electronic, and magnetic properties, due to special challenges such as strong correlations and disorder. In terms of a multicode approach, this study combines various complementary first‐principles methods based on density functional theory to exploit their specific strengths. Pseudopotential methods, known for giving reliable forces and total energies, are used for structural optimization. The optimized structure serves as input for the Green's function and linear muffin‐tin orbital methods. Those methods are powerful for the calculation of magnetic ground states and spectroscopic properties. Within the multicode approach, disorder is investigated by means of the coherent potential approximation within a Green's function method or by construction of special quasirandom structures in the framework of the pseudopotential methods. Magnetic ground states and phase transitions are studied using an effective Heisenberg model treated in terms of a Monte Carlo method, where the magnetic exchange parameters are calculated from first‐principles. The performance of the multicode approach is demonstrated with different examples, including defect formation, strained films, and surface properties.

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Study of the negative magneto-resistance of single proton-implanted lithium-doped ZnO microwires

Cited by 10 publications

References 30 publications

Conductivity fluctuations in proton-implanted ZnO microwires

Conductivity fluctuations in proton-implanted ZnO microwires

Defect‐Induced Magnetism in Nonmagnetic Oxides: Basic Principles, Experimental Evidence, and Possible Devices with ZnO and TiO₂

Magnetic and Electronic Properties of Complex Oxides from First‐Principles

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Study of the negative magneto-resistance of single proton-implanted lithium-doped ZnO microwires

Cited by 10 publications

References 30 publications

Conductivity fluctuations in proton-implanted ZnO microwires

Conductivity fluctuations in proton-implanted ZnO microwires

Defect‐Induced Magnetism in Nonmagnetic Oxides: Basic Principles, Experimental Evidence, and Possible Devices with ZnO and TiO2

Magnetic and Electronic Properties of Complex Oxides from First‐Principles

Contact Info

Product

Resources

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Defect‐Induced Magnetism in Nonmagnetic Oxides: Basic Principles, Experimental Evidence, and Possible Devices with ZnO and TiO₂