Carrier-Induced Magnetic Circular Dichloism in the Magnetoresistive Pyrochlore Tl2Mn2O7

Infrared magnetic circular dichloism (MCD), or equivalently magneto-optical Kerr effect, has been measured on the Tl2Mn2O7 pyrochlore, which is well known for exhibiting a large magnetoresistance around the Curie temperature T_C ~ 120 K. A circularly polarized, infrared synchrotron radiation is used as the light source. A pronounced MCD signal is observed exactly at the plasma edge of the reflectivity near and below T_c. However, contrary to the conventional behavior of MCD for ferromagnets, the observed MCD of Tl2Mn2O7 grows with the applied magnetic field, and not scaled with the internal magnetization. It is shown that these results can be basically understood in terms of a classical magnetoplasma resonance. The absence of a magnetization-scaled MCD indicates a weak spin-orbit coupling of the carriers in Tl2Mn2O7. We discuss the present results in terms of the microscopic electronic structures of Tl2Mn2O7.Comment: 5 pages, 5 figures, submitted to J. Phys. Soc. Jp

S-Band Transmit/Receive Antenna Systems for Automotive Satellite Applications

It happened over a hundred years ago that Henry Ford introduced his famous Model T passenger car. At that time, variants and extra features were presumably rather irrelevant compared with the automobile itself, which represented the suitable response to the need of millions of new customers [1]. Since then, a vast range of changes, func- Q3 tions, improvements, and so on were designed and eventually taken into mass production. Among those, in particular since the 1920s, car radios were introduced for commercial (broadcast) and professional (communications) purposes [2]. Wireless communications nowadays represent an important area for the car industry, for infotainment (information and entertainment), comfort, environmental and safety-related services. In the field of connectivity, and specifically in the context of antennas for wireless functions, it may be of particular relevance to consider the proposition of a new European satellite technology based on S band, namely, the Digital Video Broadcasting-Satellite Handheld standard [3] for the forward link and the European Telecommu- Q4 nications Standards Institute S-band Mobile Interactive Multimedia standard [4, 5] for the return link, both in S-Band. The mentioned standards are able to provide new satellite services for mobile terminals, such as broadcasting of radio, TV, and data contents, by using Digital Video Broadcasting-Satellite Handheld and interactive services on the return link. This paper describes the activities related to the mentioned S-band system carried out by Calearo in the frame of the COSTARS (low COst S-band receive/Transmit Antenna for vehiculaR applicationS) project, co-funded by ESA-ESTEC [6]. In particular, the authors first briefly analyze the state of the art of the services present in the car industry from the perspective of automotive antennas, analyzing the current wireless applications and considering the amount of highly integrated functionalities already present, or being proposed. Then, the design and performances of a switchable dual polarized automotive transmission/reception antenna (COSTARS project) and usable for S-band automotive applications are introduced. The paper also includes a description of the antenna industrialization and production line and the related measurements performed during the project

State of the art review for automotive satellite antennas

The number of Satellite Services have increased tremendously during the last years: although initially driven only the military applications, commercial automotive applications collected the mass market attention in the recent years. Nowadays, these satellite services are mainly used for voice, data, internet, and tracking applications. Vehicles are increasingly being equipped with on-board electronic systems, such as Global Positioning System (GPS), Mobile Phone and Digital Communication Systems (GSM, UMTS and DCS), Digital Video and Audio Broadcast Services (DVB-T, DAB), which are usually integrated together, sharing the same multiband antenna. The aim of the present article is to review the antenna solutions used in the automotive markets, providing a literature and a product overview with indications of future trends