Magnetic and magneto-optical quenching in (Mn^2+, Sr^2+) metaphosphate glasses

A Winterstein,H Akamatsu,L Wondraczek,M A Schmidt,K Tanaka,D Möncke

doi:10.1364/ome.3.000184

Abstract

Transition metal ions such as Mn2+, Fe2+, or Co2+ provide an interesting alternative to rare earth dopants in optically active glasses. In terms of their magneto-optical properties, they are not yet very well exploited. Here, we report on the effect of Mn2+ on Faraday rotation in a metaphosphate glass matrix along the join MnxSr1-x(PO3)2 with x = 0...1. Mn2+ shows small optical extinction in the visible spectral range and, compared to other transition metal ions, a high effective magnetic moment. At high Mn- levels, however, the magneto-optical activity of Mn2+ is strongly quenched due to ionic clustering. The magnetic properties of the heavily Mn2+-loaded phosphate matrix are dominated by a superexchange interaction in the Mn2+-O-Mn2+ bridge with antiparallel spin alignment between Mn2+ and O2- species. The apparent paramagnetic potential of Mn2+ species can therefore not be exploited at room temperature.

Highlights

Magneto-optics utilize the Faraday effect, by which the plane of linearly polarized light is rotated as the light propagates through a magneto-optical (MO) medium which is exposed to a longitudinal magnetic field
We report on the effect of Mn2+ on Faraday rotation in a metaphosphate glass matrix along the join MnxSr1-x(PO3)2 with x = 0
Heavily Mn2+-loaded glasses could be designed as zero-rotation materials

Summary

Introduction

Magneto-optics utilize the Faraday effect, by which the plane of linearly polarized light is rotated as the light propagates through a magneto-optical (MO) medium which is exposed to a longitudinal magnetic field. Addition of paramagnetic transition metal ions such as Mn2+, Fe2+, or Co2+ is known to affect the magnetic suscibility, antiferromagnetic behavior and magneto-optical properties of the glass [8,10,14]. While most studies or even applications which utilize magnetic properties of glasses do not require high optical transparency, even minor amounts of coloring species may have a devastating effect on the magneto-optical performance of the material. To account for this and to evaluate and compare different materials, a figure of merit (FOM) has been defined as the Faraday rotation relative to the spectral absorption α of the material, FOM =. Because Mn2+ exhibits one of the highest theoretical magnetic moments of all ion species of the TM group, we focus here on the join of MnPO3-SrPO3 which shows excellent glass formation even at very high Mn2+ content

Experimental

Results and discussion

Absorption spectroscopy

Magnetic properties

Magneto-optical quenching

Conclusions