The innovation engine for new materials

Stephanie Moffitt

Stephanie Moffitt

Major: 

Chemistry

University: 

University of California Santa Barbara

Mentor(s): 

Moureen Kemei

Faculty Sponsor(s): 

Professor Ram Seshadri

Faculty Sponsor's Department(s): 

Materials

Project Title: 

STRUCURE-PROPERY RELATIONSHIPS WITHIN Co AND Cu DOPED SAMPLES OF FRUSTRATED ZnCr2O4

Project Description: 

A solution to the ever-present demand for more powerful computers may be hidden in the form of the novel electronic and magnetic properties seen in magnetically frustrated materials. In order to harness and further develop these materials, a greater understanding of their structure-property relationships is vital. The high intensity x-rays produced at the Advanced Photon Source located at the Argonne National Lab provide a powerful probe of structural composition at temperatures varying from 6 to 300Kelvin (K). We combine these high resolution structural measurements with magnetic measurements to analyze the spin-lattice coupling which occurs in the frustrated compound ZnCr2O4. Our work shows that at about 12K both a structural distortion and the onset of long range antiferromagnetic order are seen. These concurrent structural and magnetic transitions suggests strong spin-lattice coupling in the material.  In addition to analyzing ZnCr2O4 , this work studies the dilute doping effects of magnetic ions (Cu and Co) onto the non-magnetic Zn site. We show that though the magnetic effects of these dopants are relatively similar, the structural effects are very different. Cu is a Jahn-teller active ion whose d-state degeneracy appears to cause the structural change of the material to occur at a much higher temperature. Meanwhile, Co, which lacks this additional degeneracy, appears to suppress the structural transition to a  much colder temperature beyond the sensitivity of our instrument.  Overall a greater understanding of the structural property relations and controlling factors of the frustrated system ZnCr2O4 has been achieved.