NEUTRON SCATTERING STUDIES OF MULTIFERROIC HoMnO₃

Benjamin Ueland, Owen Vajk, Jeffrey Lynn, Sang-Wook Cheong

            Modern technology depends on the ability to manipulate the electrical properties of materials in order to control, store, retrieve, and display information.  Generally, electronic devices, such as computers, perform operations solely by exploiting either the electronic charge states or electronic magnetic states of their constituent materials, limiting the number of degrees of freedom the device has available to it.  Thus, possessing materials which show much coupling between their charge and magnetic properties would be advantageous in order to further the development of more sophisticated technology.

Some such materials, known as multiferroics, have been discovered in which the manipulation of magnetically ordered states by electric fields, or manipulation of electrically ordered states by magnetic fields is realized.  However, these materials are few in number and only exhibit strong magnetoelectric coupling at relatively low temperatures.  In order to further understand the basic mechanisms present in these materials, we have performed neutron scattering experiments on multiferroic hexagonal HoMnO₃ at the NIST Center for Neutron Research (NCNR), which exhibits a ferroelectric ordering transition at T = 875 K and antiferromagnetic ordering transitions at T = 75 K and T = 4.6 K, in zero applied field.  Here, we present results from elastic and inelastic scattering experiments that show manipulation of the magnetically ordered and charge ordered states through application of either an electric or magnetic field.  Additionally, magnon dispersion relations and low lying crystalline electric field levels have been mapped out, which show the fundamental excitations present in the material.  Small angle neutron scattering (SANS) experiments have also been performed to determine the role of magnetic domains within HoMnO₃, and results from these experiments will also be presented.

Author Information:

Benjamin G. Ueland
NIST Center for Neutron Research

National Institute of Standards and Technology
100 Bureau Drive Stop 6102

Gaithersburg, MD 20899 -6102

Room :  A119

email: ben.ueland@nist.gov
Ph:  301-975-8489

Fax : 301-921-9847

Mentor :  Jeffrey Lynn

Category:  Physics

Neither I nor my mentor is a member of Sigma Xi.