Ž . Sensors and Actuators 81 2000 240–243 www.elsevier.nlrlocatersna Growth and investigation of ZnHgMnTe crystals for magnetic field sensors A.I. Savchuk a, ) , S.V. Medynskiy a , I.D. Stolyarchuk a , V.I. Fediv a , V.M. Frasunyak a , P.I. Nikitin b,1 , S.I. Nikitin c a Department of Physical Electronics, CherniÕtsi UniÕersity, 2 Kotsubynskiy St., CherniÕtsi, 274012, Ukraine b General Physics Institute, 38 VaÕiloÕ St., Moscow, 117942, Russian Federation c ChuÕashia State UniÕersity, 15 MoskoÕskiy pr., Cheboksary, 428015, Russian Federation Abstract Single crystals of Zn Hg Mn Te grown by a modified Bridgman method have been investigated by means of optical 1yxyy x y spectroscopy and the Faraday rotation techniques. It has been found that structural, optical and magnetooptical characteristics of the studied quaternary semimagnetic semiconductor with x s0.5, y s0.4 have good prospects for applications as sensing elements in magnetic field sensors. An advantage of the material, as compared with Cd Mn Te, is its better performance in the range of laser 1yx x wavelengths above 800 nm, for which cheap and low-noise laser diodes are available. q 2000 Elsevier Science S.A. All rights reserved. Keywords: Faraday rotation; Semimagnetic semiconductor; Crystal; Growth; Energy bandgap; Magnetic field sensor 1. Introduction The magnetooptical Faraday effect provides fertile ground for different applications of magnetic materials, including a variety of magnetic sensors. Recently, semi- magnetic semiconductors have been added as promising candidates for such applications owing to their giant Fara- day rotation. Among the semimagnetic semiconductors, solid solutions of Cd Mn Te are the most extensively 1yx x w x studied. In several papers 1–6 , Cd Mn Te crystals 1yx x were proposed for use as sensitive elements of magnetic field sensors. The advantage of these crystals over other Ž . materials is a wide frequency range up to 4 GHz . How- ever, at room temperatures the operating spectral range of Cd Mn Te-based magnetic field sensors is restricted by 1yx x the energy bandgap E s 1.51 eV of the binary CdTe g compound. It should be noted that it is at photon energies close to E that a significant enhancement of the Faraday g rotation takes place. This restriction can be overcome by using semimagnetic semiconductors based on the HgTe compound, which has a low E sy0.146 eV. Quaternary g semimagnetic semiconductors of the CdHgMnTe type pro- ) Corresponding author. Tel.: q 380-372-598473; Fax: 380-372-551809; E-mail: savchuk@chdu.cv.ua 1 Fax: q 7-095-1350376; E-mail: nikitin@kapella.gpi.ru. vide the additional opportunity for varying the values of the energy band parameters, which make them attractive for application in the near-infrared spectral range. In this work we discuss the peculiarities of growth, the material properties and the application of quaternary Zn Hg Mn Te crystals. 1yxyy x y 2. Crystal growth and preparation of samples The vertical Bridgman method was used for growth of Zn Hg Mn Te single crystals with x s 0.5–0.6; y s 1yxyy x y 0.3–0.4. High-purity starting components Zn, Hg, Te, with a purity of 6 N, and Mn, with a purity of 4 N, were loaded into a carbon-coated quartz ampoule having a wall thick- ness above 2 mm. The ampoule, evacuated down to 10 y6 Torr and sealed, was placed into a vertical furnace and heated at a rate of 10 Krh up to a temperature above the liquidus temperature indicated by the phase diagram. The ampoule was kept at this temperature for two days and then quenched to room temperature at a rate of 1 mmrh through a temperature gradient of 2.0–2.5 Krmm. The main difficulty during the growth process was associated with the high vapour pressure of Hg. Because of this the synthesis of ZnHgMnTe was performed by both the con- ventional separate component method and combining Zn- 0924-4247r00r$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. Ž . PII: S0924-4247 99 00132-6