Although it has been well known that materials in which both space inversion and time reversal symmetries are broken can host optical magneto-electric effect, i.e., change in optical constants with the reversal of propagating direction of light, the largest change in absorption ever reported on this effect was 0.2%. Here we show that optical absorption in noncentrosymmetric weak ferromagnetic material CuB 2 O 4 changes by more than 100% with reversal of a low magnetic field of 300 Oe. The gigantic optical magneto-electric effect is ascribed to the canted antiferromagnetic spin ordering of squarecoordinated Cu 2þ sites, where the local inversion is slightly broken. Linear magneto-electric (ME) effect -induction of magnetization by an electric field or of electric polarization by a magnetic field is anticipated in crystals which have neither space-inversion nor time-reversal symmetry.1,2) One of the intriguing effects in such ME materials is a peculiar nonreciprocal optical effect, which is a change in optical constants with the reversal of propagating direction of light.3-6) This effect can be regarded as an expansion of linear ME effects into optical frequencies. The nonreciprocal optical effect in ME materials is classified according to the type of the light polarization. For circularly polarized light, such a nonreciprocal optical effect was first observed in Cr 2 O 3 by Pisarev et al.3) and Krichevtsov et al. 4) In a Cr 2 O 3 single crystal after magneto-electric cooling process to align antiferromagnetic domain, gyrotropic birefringence was observed in transmission 3) and reflection. 4) In materials with spontaneous magnetization M s and polarization P s , a similar nonreciprocal effect, termed optical magneto-electric (OME) effect hereafter, arises when light propagates in the P s  M s direction. 5,6) This type of OME effect was reported in GaFeO 3 , in which P s and M s are along the b and c axes, respectively.5-7) The group theory predicts the existence of the bc and cb terms of linear ME tensor . Electromagnetic wave propagating along the a axis consists of electric field E ! b (E

Magnetic and structural phase diagram in a spinel-type solid solution system Fe(1-x)Mn(x)Cr(2)O(4) has been investigated. The cubic-to-tetragonal transition temperature T(s 1) is gradually reduced by the substitution of Mn(2+) (3d(5)) for Jahn-Teller-active Fe(2+) (3d(6)) ions, implying the long-range nature of the ferroic interaction between orbitals. In the paramagnetic tetragonal phase for x < 0.5, the c parameter is shorter than a because of the anharmonicity of the elastic energy. The crystal structure further changes to orthorhombic at around the ferrimagnetic transition temperature T(N 1). T(s 1) and T(N 1) meet at x = 0.5, and Mn substitution of more than 0.5 gives rise to another tetragonal phase with a < c. The systematic change in crystal structure is discussed in terms of competition between the anharmonic lattice potential and the intra-atomic spin-orbit interaction at Fe(2+).

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This paper documents the calibration of the Highway Safety Manual (HSM) safety performance function (SPF) for rural two-lane two-way roadway segments in Utah and the development of new SPFs through negative binomial regression. Crash data from 2005 to 2007 on 157 selected study segments in Utah provided a 3-year frequency of observed crashes to calibrate the HSM SPF and develop new models. The calibration factor for the HSM SPF for rural two-lane two-way roads in Utah is 1.16, indicating that the original HSM model under predicts crashes in Utah. The HSM suggests that jurisdiction-specific SPFs may predict crashes with greater reliability than calibrated SPFs. The following variables were significant in each of the four models developed by this research: annual average daily traffic (AADT), segment length, speed limit, and the percentage of AADT composed of multiple-unit trucks. AADT and segment length are used in the HSM SPF; speed limit and the percentage of AADT composed of multiple-unit trucks were found to correlate significantly with observed crash frequencies. The fourth negative binomial model developed in the study would be the best SPF to predict crashes on rural highways in Utah. As encouraged by the HSM and contemporary research, the empirical Bayes method can be applied with each jurisdiction-specific SPF because the analysis provided an overdispersion parameter for each model.

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The modification of linear birefringence through electro- and piezo-optical effects has been applied in optical devices. In contrast, the control of linear birefringence by a magnetic field is not practically utilized since conventional magnetic linear birefringence is a second-order small effect. We report an approach to control linear birefringence with a first-order optical magneto-electric effect. The effect can provide a new type of phase retarder, which is magnetically controllable and propagation-direction dependent.

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