TY - JOUR
T1 - Structure and magnetic properties of NdFeB thin films with Cr, Mo, Nb, Ta, Ti, and V buffer layers
AU - Jiang, H.
AU - O'Shea, M. J.
N1 - Funding Information:
This work was supported by the Army Research Office under grant no. DAAG55-98-1-0274 and By the Kansas Technology Enterprise Corporation. We are grateful to Professor Mickey Ransom (Department of Agronomy, KSU) for assistance with X-ray diffraction and Dr. Shaole Wu (Materials Characterization Lab., Penn State University) for assistance with ICP analysis.
PY - 2000/3
Y1 - 2000/3
N2 - Layers of NdFeB of the form A(20 nm)/NdFeB(d nm)/A(20 nm) where A represents Cr, Mo, Nb, Ta, Ti, V were prepared on a silicon substrate by magnetron sputtering. The purpose is to determine how (i) the chosen buffer layer and (ii) NdFeB layer thickness d (especially d < 200 nm) effect the structure, morphology and magnetic properties of NdFeB films. Films are annealed for 20 min and a few selected films are subjected to a rapid thermal anneal for 30 s. Other parameters (deposition rate, NdFeB composition) were held constant and we did not attempt to optimize these. After a 20 min anneal above 500°C the main crystalline phase present is Nd2Fe14B with no preferred crystalline orientation. Our highest coercivities occur for buffer layer elements from row five of the periodic table, 20 kOe (1600 kA/m) in a Nb buffered sample with d of 180 nm and 17 kOe (1350 kA/m) in a Mo buffered sample with d of 180 nm. Buffer layers from row four (Ti, V, and Cr) and row six (Ta) all give lower coercivities. Our largest energy product, 10.3 MG-Oe (82 kJ/m3), is obtained for the Mo buffered sample. Average Nd2Fe14B crystallite size for this sample is 27 nm. Only the Cr and Ti buffered films show a large coercivity (≥ 2 kOe) for d of 54 nm with the Cr films showing the highest coercivity, 2.7 kOe (215 kA/m). In films subjected to a rapid thermal anneal (anneal time 30 s) we find that both the coercivity and energy product are larger than in samples subjected to a 20 min anneal. In our Nb buffered systems we obtain coercivities as high as 26.3 kOe (2090 kA/m) after a rapid thermal anneal.
AB - Layers of NdFeB of the form A(20 nm)/NdFeB(d nm)/A(20 nm) where A represents Cr, Mo, Nb, Ta, Ti, V were prepared on a silicon substrate by magnetron sputtering. The purpose is to determine how (i) the chosen buffer layer and (ii) NdFeB layer thickness d (especially d < 200 nm) effect the structure, morphology and magnetic properties of NdFeB films. Films are annealed for 20 min and a few selected films are subjected to a rapid thermal anneal for 30 s. Other parameters (deposition rate, NdFeB composition) were held constant and we did not attempt to optimize these. After a 20 min anneal above 500°C the main crystalline phase present is Nd2Fe14B with no preferred crystalline orientation. Our highest coercivities occur for buffer layer elements from row five of the periodic table, 20 kOe (1600 kA/m) in a Nb buffered sample with d of 180 nm and 17 kOe (1350 kA/m) in a Mo buffered sample with d of 180 nm. Buffer layers from row four (Ti, V, and Cr) and row six (Ta) all give lower coercivities. Our largest energy product, 10.3 MG-Oe (82 kJ/m3), is obtained for the Mo buffered sample. Average Nd2Fe14B crystallite size for this sample is 27 nm. Only the Cr and Ti buffered films show a large coercivity (≥ 2 kOe) for d of 54 nm with the Cr films showing the highest coercivity, 2.7 kOe (215 kA/m). In films subjected to a rapid thermal anneal (anneal time 30 s) we find that both the coercivity and energy product are larger than in samples subjected to a 20 min anneal. In our Nb buffered systems we obtain coercivities as high as 26.3 kOe (2090 kA/m) after a rapid thermal anneal.
UR - http://www.scopus.com/inward/record.url?scp=0033890694&partnerID=8YFLogxK
U2 - 10.1016/S0304-8853(99)00789-1
DO - 10.1016/S0304-8853(99)00789-1
M3 - Article
AN - SCOPUS:0033890694
SN - 0304-8853
VL - 212
SP - 59
EP - 68
JO - Journal of Magnetism and Magnetic Materials
JF - Journal of Magnetism and Magnetic Materials
IS - 1
ER -