arXiv subjects

R. Höhne

Publications and source records attributed to R. Höhne.

5 recordsLinked to original sources

arXiv2008

A comparison of the magnetic properties of Proton- and Iron-implanted graphite

In this work we have investigated the changes of the magnetic properties of highly oriented pyrolytic graphite samples after irradiation either with $\sim 3 \times 10^{14}$ protons or $ 3.5 \times 10^{13} ... 3.5 \times 10^{14}$ iron ions with energies in the MeV range. Our results show that iron and proton irradiations can produce similar paramagnetic contributions depending on the implantation temperature. However, only protons induce a ferromagnetic effect.

cond-mat.str-el↗

arXiv2005

Induced Magnetic Order by Ion Irradiation of Carbon-Based Structures

In this chapter we review the magnetic effects produced by proton irradiation on graphite, disordered carbon and fullerene films. The advantage of proton irradiation is twofold: it enables us to make an impurity analysis simultaneously to the implantation of hydrogen. In this chapter we will review the main effects obtained after proton irradiation in different carbon-based structures. This chapter is organized as follows. In section 2 we provide the main characteristics of our irradiation facility. In this section we show an example of element analysis obtained in one of the graphite samples used for the irradiation studies. The irradiation effects are reviewed in section 3. This section is divided in two main subsections that describe the effects in oriented graphite and carbon-based thin films. In section 4 we discuss some of the effects observed after annealing the sample at high temperatures in vacuum or after leaving it at room temperature for a long period of time.

cond-mat.mtrl-sci↗

arXiv2004

Searching for a magnetic proximity effect in magnetite-carbon structures

In order to study a possible magnetic proximity effect in magnetite-carbon structures, we have performed magnetization measurements of graphite-magnetite composites with different mass ratios as well as the measurement of the magnetoresistance of one of them and of the magnetization of a magnetite-carbon bilayer. The overall results do not indicate the induction of bulk ferromagnetism in graphite and disordered carbon structures through their contact with magnetite.

cond-mat.mtrl-sci↗

arXiv2003

Induced Magnetic Ordering by Proton Irradiation in Graphite

We provide evidence that proton irradiation of energy 2.25 MeV on highly-oriented pyrolytic graphite samples triggers ferro- or ferrimagnetism. Measurements performed with a superconducting quantum interferometer device (SQUID) and magnetic force microscopy (MFM) reveal that the magnetic ordering is stable at room temperature.

cond-mat.str-el↗

arXiv2000

Magnetic-Field-Driven Superconductor-Insulator-Type Transition in Graphite

A magnetic-field-driven transition from metallic- to semiconducting-type behavior in the basal-plane resistance takes place in highly oriented pyrolytic graphite at a field $H_c \sim 1~$kOe applied along the hexagonal c-axis. The analysis of the data reveals a striking similarity between this transition and that measured in thin-film superconductors and Si MOSFET's. However, in contrast to those materials, the transition in graphite is observable at almost two orders of magnitude higher temperatures.

cond-mat.str-el↗