Encryption is widely used in storage systems to hide data contents. Unfortunately, when a powerful adversary coerces an authorized user to reveal encryption keys, encryption fails to hide the existence of the encrypted sensitive data. To meet the requirements of data protection, plausible deniability (PD) has been proposed to protect sensitive data. However, building existing PD mechanisms on the emerging interlaced magnetic recording (IMR) based hard disk drive, is challenging. In this paper, we propose SecureIMR, the first practical PD system on IMR-based devices. SecureIMR incorporates deniability into IMR disk device controller. SecureIMR accommodates the special nature of IMR (e.g., the interlaced tracks) to achieve plausible deniability, while providing the trade-off between storage performance and deniability overheads. Our comprehensive evaluation demonstrates that SecureIMR maintains strong security guarantees while incurring minimal performance overhead compared to conventional non-PD IMR storage systems. The results show that, compared with conventional non-PD IMR storage, SecureIMR only incurs a small overhead.