The magnetic and recording properties of CoCrTa/Cr longitudinal magnetic recording media with various Cr contents have been investigated by changing the Cr underlayer thickness, CoCrTa magnetic layer thickness and deposition temperature. The composition of CoCrTa alloy targets was $CoCr_{10.11}Ta_{2.07},\; CoCr_{11.92}Ta_{2.08}$ and $CoCr_{13.77}Ta_{1.84}$ respectively. The films were deposited on textured NiP/Al-Mg substrates by DC magnetron sputtering. The thickness of films was determined by DEKTAK IID and X-ray fluorescence thin film measuring system. Magnetic properties were measured using a vibrating sample magnetometer. For the purpose of analyzing the behavior of crystal growth and surface morphology, x-ray diffractometer and scanning electron microscopy were used. Recording characteristics have been evaluated with Guzik RWA301B. As the T$_\mbox{sub}$ increase, the coercivity and O.R. of the films with CoCrTa($600\mbox{\AA}$)/Cr($700\mbox{\AA}$) are increased. The changes in Hc with T$_\mbox{sub}$ may be associated with grain boundary segregation of Cr. As the Cr thickness increase from 0 to 500 $\mbox{\AA}$, the Hc are sharply increased from 400 to 1600 Oe. Above $500\mbox{\AA}$ thickness, the Hc value changes little. The [OR]$_\mbox{Hc}$ also sharply increases when Cr thickness is below $500\mbox{\AA}$ and then it decreases with further increase in Cr thickness. The S$^\ast$ changes little with various Cr thickness. Its value ranges about 0.8. As the Cr thickness increase, the grain size of CoCrTa film are increased. It seems not that the grain size is the major factor of coercivity increasing. The XRD patterns of $CoCr_{10.11}Ta_{2.07}(600 \mbox{\AA})/Cr$ double layer depostied at $290\,^\circ\!C$ without Cr underlayer reveal a broad peak with highest intensity near $2\theta = 44.4^\circ$ and the XRD patterns with Cr underlayer show CoCrTa(10 $\bar{1}$ 0) and 10 $\bar{11}$) peaks from Cr(110). The sharp increase of Hc and O.R. with the increase of $\delta_{Cr}$ might result from the formation of (10 10$\bar{10}$) and (10 $\bar{10}$) texture of the magnetic layer on (110)Cr plane. The maximum Hc of the films with a $700 \mbox{\AA}$ Cr thickness, deposited at $290\,^\circ\!C$, is about 1600 Oe, at which the thickness of CoCrTa is about $400 \mbox{\AA}$ and then Hc with the increase of CoCrTa magnetic layer thickness decreases. It seems that the reason for lower Hc above $400 \mbox{\AA}$ thickness could be the decrease of the degree of crystal texture, resulting in smaller in-plane anisotropy. The SNR rapidly increases between 100 and $200\,^\circ\!C$ and maintains its value at 32 dB above $200\,^\circ\!C$. The bit shift decreases with the increase of $T_{sub}$ upto $250\,^\circ\!C$ and keeps the value about 10 ns above $250\,^\circ\!C$. The SNR may be mainly decided by the Hc value with similar $S^\ast$. The SNR of CoCrTa/Cr double layer has a maximum value(33 dB) at the Cr underlayer thickness about $700\mbox{\AA}$. The increase of SNR may be attributed to the decrease of coupling force among ferromagnetic grain in CoCrTa magnetic layer due to promotion of column separation in the Cr underlayer. The bit shift has a minimum value (9 ns) near the Cr underlayer thickness of $700\mbox{\AA}$. As the CoCrTa thickness increases the SNR increases monotonically. The reason for higher SNR may be the increase of Mr $\times \delta$ as the Co content increase in the magnetic films. The bit shift decreases as the CoCrTa thickness increases. It has a minimum value near $600\mbox{\AA}$ and it is clear that the bit shift of 10 at\%Cr film is lower than other compostion between 400 and $600\mbox{\AA}$. The results of PW50, O/W, SNR and bit shift are presented that the best recording properties can be achievable when the CoCrTa thickness was between 400 and $600\mbox{\AA}$ and the Cr underlayer thickness was between 500 and $700\mbox{\AA}$. The magnetic properties of three compositions have not clear distinction, however, the recording characteristics of $CoCr_{10.11}Ta_{2.07}$ are presented the best recording characteristics in three composition magnetic films.
