Room-Temperature Ferromagnetism in a II-VI Diluted Magnetic Semiconductor ${\mathrm{Z}\mathrm{n}}_{1-x}{\mathrm{C}\mathrm{r}}_x\mathrm{T}\mathrm{e}$

The magnetic and magneto-optical properties of a Cr-doped II-VI semiconductor ZnTe were investigated. Magnetic circular dichroism measurements showed a strong interaction between the $sp$ carriers and localized $d$ spins, indicating that ${\mathrm{Z}\mathrm{n}}_{1-x}{\mathrm{C}\mathrm{r}}_x\mathrm{T}\mathrm{e}$ is a diluted magnetic semiconductor. The Curie temperature of the film with $x=0.20$ was estimated to be $300\pm 10\mathrm{K}$, which is the highest value ever reported for a diluted magnetic semiconductor in which $sp\mathrm{\text{−}}d$ interactions were confirmed. In spite of its high Curie temperature, ${\mathrm{Z}\mathrm{n}}_{1-x}{\mathrm{C}\mathrm{r}}_x\mathrm{T}\mathrm{e}$ film shows semiconducting electrical transport properties.

Figure 1

Magnetization curves of ${\mathrm{Z}\mathrm{n}}_{1-x}{\mathrm{C}\mathrm{r}}_x\mathrm{T}\mathrm{e}$ ($x=0.20$) film at various $T$. The inset shows the Arrott plots of the magnetization data.

Figure 2

MCD spectra of (a) room-temperature ferromagnetic compound CrTe film, (b) 100-nm thick ZnTe film, (c) 80-nm thick ${\mathrm{Z}\mathrm{n}}_{1-x}{\mathrm{C}\mathrm{r}}_x\mathrm{T}\mathrm{e}$ ($x=0.20$) film on ZnTe buffer with several monolayers, and (d) 400-nm thick ${\mathrm{Z}\mathrm{n}}_{1-x}{\mathrm{C}\mathrm{r}}_x\mathrm{T}\mathrm{e}$ ($x=0.20$) film on 200-nm thick ZnTe buffer at $T=20\mathrm{K}$ and ${\mu }_{0}H=1\mathrm{T}$. MCD spectra of both 80- and 400-nm thick ${\mathrm{Z}\mathrm{n}}_{1-x}{\mathrm{C}\mathrm{r}}_x\mathrm{T}\mathrm{e}$ ($x=0.20$) films at $T=20\mathrm{K}$ measured in any magnetic fields can be superposed upon a single spectrum over the whole photon energy range [(${\mathrm{c}}^{\prime }$) and (${\mathrm{d}}^{\prime }$)].

Figure 3

Magnetic field dependence of MCD intensity of ${\mathrm{Z}\mathrm{n}}_{1-x}{\mathrm{C}\mathrm{r}}_x\mathrm{T}\mathrm{e}$ ($x=0.20$) film at $E=2.2\mathrm{e}\mathrm{V}$ and $T=20\mathrm{K}$ and 293 K.

Figure 4

Arrott plots of MCD intensity of ${\mathrm{Z}\mathrm{n}}_{1-x}{\mathrm{C}\mathrm{r}}_x\mathrm{T}\mathrm{e}$ ($x=0.20$) film at $E=2.2\mathrm{e}\mathrm{V}$ and various $T$. The inset shows the temperature dependence of MCD intensity (open circles) extrapolated to ${\mu }_{0}H=\mathrm{T}$ obtained by the Arrott plot, together with that of $M_S$ (solid circles).